LECTURE 1Introduction to Acoustical Design
Matias Remes MSc FISE A acoustics
Rak-433415 Building Physics Design 2
ACOUSTICAL DESIGNAutumn 2015
Course arrangements
Schedule
bull Lectures (6) 89-1310 Tue 1615-20 in hall R2 main themesndash 89 Lecture 1 Introduction basic concepts of acoustics
ndash 159 Lecture 2 Airborne sound insulation
ndash 229 Lecture 3 Impact sound insulation
ndash 299 Lecture 4 Room acoustics
ndash 610 Lecture 5 HVAC noise control vibration isolation
ndash 1310 Lecture 6 Traffic noise guidelines and regulations
bull Exercises (5) 149-1210 Mon 1615-18 in hall R2
bull Design exercise notified later
bull Exam 16122015 (20102015 for students from previousyears)
Execution
bull Compulsory
ndash Design exercise
ndash Exam
bull Recommended and desirable
ndash Attending lectures
ndash Solving exercies independently at home
bull Course books
ndash RIL 243-1-2007 (only available in
Finnish)
ndash Master Handbook of Acoustics
EverestampPohlman (a few sections to be
notified later)
The scope of acoustics
[Lindsay 1964 muutettu]
[Lindsay`s wheel of acoustics
1964 modified Remes]
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Course arrangements
Schedule
bull Lectures (6) 89-1310 Tue 1615-20 in hall R2 main themesndash 89 Lecture 1 Introduction basic concepts of acoustics
ndash 159 Lecture 2 Airborne sound insulation
ndash 229 Lecture 3 Impact sound insulation
ndash 299 Lecture 4 Room acoustics
ndash 610 Lecture 5 HVAC noise control vibration isolation
ndash 1310 Lecture 6 Traffic noise guidelines and regulations
bull Exercises (5) 149-1210 Mon 1615-18 in hall R2
bull Design exercise notified later
bull Exam 16122015 (20102015 for students from previousyears)
Execution
bull Compulsory
ndash Design exercise
ndash Exam
bull Recommended and desirable
ndash Attending lectures
ndash Solving exercies independently at home
bull Course books
ndash RIL 243-1-2007 (only available in
Finnish)
ndash Master Handbook of Acoustics
EverestampPohlman (a few sections to be
notified later)
The scope of acoustics
[Lindsay 1964 muutettu]
[Lindsay`s wheel of acoustics
1964 modified Remes]
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Schedule
bull Lectures (6) 89-1310 Tue 1615-20 in hall R2 main themesndash 89 Lecture 1 Introduction basic concepts of acoustics
ndash 159 Lecture 2 Airborne sound insulation
ndash 229 Lecture 3 Impact sound insulation
ndash 299 Lecture 4 Room acoustics
ndash 610 Lecture 5 HVAC noise control vibration isolation
ndash 1310 Lecture 6 Traffic noise guidelines and regulations
bull Exercises (5) 149-1210 Mon 1615-18 in hall R2
bull Design exercise notified later
bull Exam 16122015 (20102015 for students from previousyears)
Execution
bull Compulsory
ndash Design exercise
ndash Exam
bull Recommended and desirable
ndash Attending lectures
ndash Solving exercies independently at home
bull Course books
ndash RIL 243-1-2007 (only available in
Finnish)
ndash Master Handbook of Acoustics
EverestampPohlman (a few sections to be
notified later)
The scope of acoustics
[Lindsay 1964 muutettu]
[Lindsay`s wheel of acoustics
1964 modified Remes]
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Execution
bull Compulsory
ndash Design exercise
ndash Exam
bull Recommended and desirable
ndash Attending lectures
ndash Solving exercies independently at home
bull Course books
ndash RIL 243-1-2007 (only available in
Finnish)
ndash Master Handbook of Acoustics
EverestampPohlman (a few sections to be
notified later)
The scope of acoustics
[Lindsay 1964 muutettu]
[Lindsay`s wheel of acoustics
1964 modified Remes]
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
The scope of acoustics
[Lindsay 1964 muutettu]
[Lindsay`s wheel of acoustics
1964 modified Remes]
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
[Lindsay 1964 muutettu]
[Lindsay`s wheel of acoustics
1964 modified Remes]
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Brief history of acoustics
rdquoAcoustics is a science of the last thirty yearsrdquo
Physicist Dayton Miller 1931
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
History
bull 6th century BCPythagoras investigates the relation between the length and pitch of strings
bull 325 BCAristotle writes about the production and reception of sound and echoes
bull 27 ADMarcus Vitruvius Pollio De Architectura first instructions on the acoustic design of theaters
bull 800s Islamic culture produces new knowledge on sound-related phenomena(eg hearing and speech production)
bull 1500sThe effects of Renaissance cathedrals on music
Creek aκουειν = rdquoto hearrdquo
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
History
bull Mid 1600s
Sound reflection and echoes are explained as analog to the reflection of light R Boyle ja R Hooke deduce that sound needs a medium in order to propagate G Galilei investigates the vibrationof strings
bull 1670`sFirst purpose-built concert hall is finished in London
bull 1700sCommercialisation of music and theatre industry creates new social and acoustical framework
bull 1816
P S Laplace discovers the equation for calculating the speed of sound (Newton attempted this before but did not get the right result)
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
History
bull Beginning of 1800s
Practical research on the behaviour of sound in enclosed spaces(background growing need for auditoria and development of orchestralmusic) C Bullfinch R Mills and J S Russell develop methods for improving speech intelligibility in rooms
bull 1850
Joseph Henry discovers the Precedence effect and evaluates that the shape of the room does not explain alone the way it sound but materialshave to be considered also
bull 1860s
Hermann von Helmholtz investigates speech production sense of hearingand sound disturbance
bull 1876
A G Bell invents the microphone (however condensator microphone is notinvented until 1916)
bull 1877
Lord Rayleigh The Theory of Sound the mathematical principles of sound and vibration
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
History
bull End of 1800sWallace Clement Sabine hired to improve the acoustics of the Fogg Art Museum in Harvard
Sabine invents a method for measuring the reverberation timeof a room using an organ pipe and stopwatch
Sabine equation for calculating the reverberation time
bull 1895W C Sabine as acoustical designer of the Boston Symphony Hall
bull 1920Efirst patented acoustical tile
bull 1927First anechoic chamber built (F Watson)
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
History
bull 1930s
First sound level meter (P Sabine)
bull 1930s
Suggestions for sound insulation regulations in several countries measurement of and methods to decrease traffic noise in largecities
acoustics becomes a tool for humans to control the environment
bull 1943
The Finnish Aumlaumlniteknillinen yhditys (now Akustinen Seura Acoustical Society of Finland) is established
the field of acoustical expertise in Finland expands teachingacoustics begins gradually in the 1950s and 1960s
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics as a field of science and
technologybull Old field of science but significant effects not until the 20th century
bull Acoustics has enabled egndash Telephone radio recording and reproduction of sound talking movies
ndash Hearing protection in industrial labour
ndash Privacy in residential buildings
ndash The building of spaces which work according to desired function
bull Sound plays an important role in how people experience and perceive the surrounding environmentndash Hearing
ndash Speech communication
ndash Music
ndash Warning signals
ndash Sound in nature
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustical design of buildings
rdquo Akustinen suunnittelu on suoritettava samanaikaisesti yleisen suunnittelutyoumln yhteydessauml jotta saadaan
estetyksi sellaiset ratkaisut jotka estaumlvaumlt optimaalisten akustisten tulosten saavuttamisenrdquo
Tekniikan lisensiaatti Eero Lampio 1962
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
The rdquofour-fieldrdquo of acoustical design
Acoustical design of buildings
(Architecturalacoustics)
Roomacoustics
Building acoustics
Noisecontrol
Vibrationisolation
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
The rdquofour-fieldrdquo of acoustical design
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Room acoustics
bull rdquoGood room acousticsmeans that speech and music is perceived as beautiful natural and clear in every point of the roomrdquo
Engineer U Varjo 1938
bull The reflection attennuation and propagation of sound in a space
bull Goal sound (speech orchestra etc) soundsas is required by the use of space
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Building acoustics 13
bull Transition of sound between spaces via structuresndash Not only through the
separating structure butalso as flankingtransmission and throughholes etc
bull 3 parts depending on the nature of the sound sourcendash Airborne sound insulation
ndash Impact sound insulation
ndash Structure-borne sound insulation
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Building acoustics 23
bull Sound insulationndash Between spaces
(airborne and impact)
ndash From inside to outside and viceversa
ndash Equipment noise
ndash Vibration
bull Choosing the construction type is also acoustic design
Rakenteiden
ilmaaumlaumlneneristaumlvyyksiauml
0
5
10
15
20
25
30
35
40
45
50
50
80
12
5
20
0
31
5
50
0
80
0
12
50
20
00
31
50
Taajuus [Hz]
R [d
B]
Kipsilevy 2 x 13 mm (18 kgm2)
Puu 50 mm (25 kgm2)
Kevytbetoni 68 mm (27 kgm2)
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Building acoustics 33
bull Airborne sound (ilmaaumlaumlni) is sound produced in and propagated in air whereas structure-borne sound (runkoaumlaumlni) propagates in structures
bull Speech is airborne soundbull Sounds caused by walking or
dropping objects on the floor areimpact sound (askelaumlaumlni)
bull Piano produces airborne sound and structure-borne sound through itsfeet which are in contact with the floor structure
bull All technical equipment produce bothairborne and structure-borne sound
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Noise control 12
bull Outdoor noise sources
road railway and
airplane traffic
bull Indoor noise sources
machinery and service
equipment (talotekniikka)
bull Goal to diminish the
production and
propagation of noise
Kuva Salter 1999
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Noise control 22
bull HVAC equipmentndash outdoors
ndash indoors
bull Traffic noisendash Road traffic
ndash Railway traffic
ndash Airplane traffic
bull Machinery industry
bull Measurement of noiseemission
bull Noise modelling
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Vibration isolation 12
rdquoAumllkoumloumln kukaanhellip pitaumlkouml varastoa tai kaumlyttaumlkouml kiinteistoumlauml niin ettauml
naapuri taikka muuhellip kaumlrsii siitauml pysyvaumlistauml kohtuutonta rasitusta
kuten kipinoumliden tuhkan noen savun
laumlmmoumln loumlyhkaumln kaasujen houmlyryn
taumlrinaumln jyskeen taikka muun sellaisen kauttardquo
Laki eraumlistauml naapuruussuhteista 1920
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Vibration isolation 22
bull All machinery in
contact with the
building frame vibrate
and produce sound
bull Goal to diminish the
propagation of the
vibration energy by
isolating the machine
from the building
frame using elastic
building elements
Saumlhkoumljohto vapaasti riippuvana lenkkinauml
PallotasainPallotasain
BetonimassaTaumlrinaumlneristimet
Betonilaatta 250 mm
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Goals os acoustical design
bull Suitability to intended usendash Suitability to speech music
ndash Appropriate sound insulationbetween spaces
bull Healthinessndash Hearing lossndash Acoustic ergonomy
bull Comfortndash Living spaces in noisy areasndash Connection between acoustics and
aesthetics
bull (rdquowow-factorrdquo)ndash Concert halls etc Kuokkala church 2010
Lassila Hirvilammi Arkkitehdit
Helimaumlki Acoustics
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Significance of acoustical design 13
bull The starting points of acoustic design
1 Healthiness
2 Comfort
3 Use of space
bull Achieving good acoustical conditions in a buildingrequires that all the points are taken into consideration
bull The need of acoustical design is not limited to demanding spaces such as concert halls but acousticaldesign is needed in everyday buildings as well (when eg choosing the construction type of a sound-insulating structure in a school or residential building)
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Significance of acoustical design 23
bull Sound constitutes a significant part of the human
sensory environment
bull Noise (rdquounwanted soundrdquo) has significant physiological
anf psychological effects on humans
ndash Research has been extensive from the beginning if the 20th
century
ndash The effects of noise are not limited to loud noise (hearing
damage risk) but also a quiet sound can be perceived as noise
if it for example hinders concentration
bull Bad acoustics also has economic consequences
Akustiikka 1011
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Significance of acoustical design 33Investing in acoustics is worth it
bull A space which does not function acoustically as required byits use is a stranded investment ie bad business
bull Improving the acoustical conditions in a finished building is always expensivendash Meetings
ndash Measurementsndash Work of expertsndash Work spent by the user to solve the problem
ndash Larger design costsndash Larger building costs
bull Savings earned during the use of the buildingndash The effects of acoustics on working conditions
ndash There is no need to do changes to a space which works as intended
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Regulations and instruction in acoustics
bull The National Building Code of Finland Section C1-1998
bull The National Building Code of Finland Section D2-2010
bull Asumisterveysohje (2003) by the Ministry of Social Affairsand Health
bull Government Decision on the Noise Level Guide Values (9931992)
bull Acoustic Clasification of Spaces in Buildings standard SFS 5907
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics in the building project
Acoustics should be considered in the building project as soon
as possible ndash the sooner the more demanding the project is
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics in the building project Project planning phase (hankesuunnittelu)
bull Sound insulationndash Appropriate level of sound insulation according to use of spacesndash Space program (tilaohjelma) positioning of noisy quiet spaces
bull Room acousticsndash Use of space surface area volume shape room acoustical
materials
bull Control of HVAC noisendash Determine the permitted noise levelsndash Space needs required by noise control measures (silencers etc)
positioning of engine rooms and noisy machinery
bull Control of traffic noisendash Noise surveys ( recommendations eg for positioning of
buildings estimate of the need for facade sound insulation(ulkovaipan aumlaumlneneristys UAumlE)
ndash Vibration surveys
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics in the building project Preliminary design phase (luonnossuunnittelu)
bull Sound insulationndash Definition of sound insulation target valuesndash Construction types of separating and flanking structures sound insulation
requirements of doors floor coverings
bull Room acousticsndash Basic shape of speech and performance spaces room acoustical requirements
as technical values (eg reverberation time)ndash Amounts and types of room acoustical materials furnishings and decoration
bull Control of HVAC noisendash Permitted HVAC noise levels according to the uses of spaces and principles of
how the target values can be fulfilled selection of sewer system
bull Control of traffic noisendash More accurate noise survey (requirements for facade sound insulation balcony
glazings noise barriers) effects of vibration surveysndash Determination of construction types exterior wall (US) roof (YP) (sufficient
sound insulation for a given use)ndash Facade sound insulation survey (ulkovaipan aumlaumlneneristys UAumlE)
Cost for the project
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics in the building project Implementation planning phase (toteutus-) 13
bull Control of traffic noisendash FSS (facade sound insulation survey) ready in time bofore ordering
windows and doors (unless already required in the building permit phase) supplementations andor correctiong to FSS if needed
ndash Final selection of noise barries Meluesteiden lopullinen valinta (in collaboration with the architect)
bull Sound insulationndash Presentation of the details of structural joints for the structural designer
drawing of details if needed
ndash Supervision of structutal design so as to ensure that the sound insulation of joints and building elements corresponds to set requirements
bull Room acousticsndash Positioning of room acoustical materials in different spaces to the
architect approval of furnishings etc selected by the interior designer
ndash Structural designer checks the possible effects of room acoustical materials assigned to the surfaces US YP etc structures
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics in the building project Implementation planning phase (toteutus-) 23
bull Control of HVAC noisendash HVAC designer presents the acoustical designer pressure drop
calculations equipment lists HVAC drawings and noise data on all equipment fans etc
ndash Sound insulation of machine room structures noise level caused by HVAC equipment to inside spaces and outside sound insulation through ducts determination of duct silencers
ndash Selection of vibration isolators for techical equipment and implementation of vibration isolation (principles)
ndash Periaatepiirustukset and instructions of pass-throughs (LAumlPIVIENNIT) and sealings ducts electrical installations heating pipes etc possible elastic couplings (LIITOSOSA) and brackets
All information either to documents of other designers or to an acoustical specification (tyoumlselitys) which is distrubuted to all building contractors
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Acoustics in the building project Implementation planning phase (toteutus-) 33
bull Training of construction workers if neededndash Why is something donendash What is important from the acoustical viewpoint
bull Check the effects of possible changes to plansndash Construction types details changes occuring on the building
sitendash Changes due to selection of HVAC equipment (typically affect
the design of silencers)ndash Inspection of vibration isolators
bull Site supervision and inspection visits in demanding projects
bull Control measurements
Implementation according to plans
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound as a physical phenomenon
basic concepts of acousticsrdquoAkustiikassa on esitettaumlvauml suureita joiden suuruudet ja
vaumlliset suhteet vaihtelevat erittaumlin paljon Taumlmaumln johdosta on otettu kaumlyttoumloumln logaritminen asteikko johon meidaumln nyt on tutustuttava ennen kuin voimme jatkaardquo
Yli-insinoumloumlri Paavo Arni 1949
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
What is sound
bull Changes in air pressure in relation to static air pressure
bull In air sound propagates as longitudinal wave motion
Kuvat Everest amp Pohlman 2011
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound pressure level (SPL)
bull Sound pressure p = change in air pressure in relation to
static air pressure (ca 100 kPa)
bull Smallest detectable sound pressure p0 = 20 μPa
bull Sound pressure corresponding to treshold of pain 20
Pa
bull Sound pressure level [dB]
0
2
0
2
lg20lg10p
p
p
pLp
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Frequency and wavelength
bull Frequency f [Hz] = number of
vibrations per time unit
bull Normal hearing range ca 20 ndash
20000 Hz
bull Relation between frequency and
wavelength
bull c = speed of sound
(343 ms in air T = 20 degC)
Kuva Hongisto 2011
f
ccf
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Frequency ranges in acoustics
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
The function of ear
[Egan 2007]
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sensitivity of hearing
rdquoequal loudness contoursrdquo
(ISO 226)
Hearing
treshold
Sensitivity of hearing to
different frequencies is
not constant
Must be considered
when eg evaluating the
noise annoyance
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Frequency bandsOctave bands
0
20
40
60
80
100
120
16 315 63 125 250 500 1000 2000 4000 8000 16000
Oktaavikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Frequency bands One-third octave bands
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
A-weighting
-80
-60
-40
-20
0
20
40
60
80
100
120125 16
20
25
315 40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1250
1600
2000
2500
3150
4000
5000
6300
8000
10000
12500
16000
20000
Terssikaistan keskitaajuus [Hz]
Aumlaumlnenpain
eta
so [
dB]
Painottamaton keskiaumlaumlnitaso A-painotettu keskiaumlaumlnitaso A-painotus
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
A-weighting
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound level
bull Due to practical reasons the sound pressure level
measured in the whole frequency range using A-
weighting is usually given as a single number
bull This single number quantity is called sound level
(aumlaumlnitaso) and denoted as LA
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
S
O
U
N
D
L
E
V
E
L
S
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Equivalent and maximum sound level
bull Some of the sound sources in built environment producesteady and continuous noise (eg air conditioning) others act intermittently and instantaneously
both long-term equivalent (= average) and instantaneousmaximum sound level must be considered
bull Equivalent sound level LAeqT [dB] (keskiaumlaumlnitaso) is the
average sound level during the investigated time period T
bull Maximum sound level LAmax [dB] (enimmaumlisaumlaumlnitaso) is the instantaneous peak value of the sound level during the investigated time period
i
L
iiAT
TL
10
TeqA10
1lg10
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Addition of sound levels
bull Generally for two sound sources (Lp1 ja Lp2)
bull For N sound sources
bull The formulas apply to non-correlating sound sources
ie when the phases of the sound waves are
independent of each other this condition is true for all
every-day sound sources
1010 21
1010lg10 pp
totp
LLL
N
n
L np
totpL
1
10
10lg10
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Addition of sound levels
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Addition of sound levels
bull If the difference between sound levels exceeds 10 dB
the louder sound practically determines the total sound
level
[Figure Hongisto 2011]
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound power level (aumlaumlnitehotaso)
bull Sound power W [W] = the ability of a sound source to produce sound
bull Sound power corresponding to hearing treshold W0 = 1 pW
bull Sound power level LW [dB]
bull Sound power or sound power level is not directly measurablequantity but it must be determined by calculation eg fromthe sound pressure level measured at a known distance fromthe sound source
bull Note Sound power level is a property of the sound sourceand does not depend on the environment
0
lg10W
WLW
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound intensity level (intensiteettitaso)
bull Sound intensity I [Wm2] = power per unit area
bull Intensity corresponding to hearing treshold 1 pWm2
bull Sound intensity level
bull The relation between sound intensity and power
where S is surface area [m2]
0
lg10I
ILI
ISW
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Measurement of sound power level
bull Sound power level can be determied by measuring the
average intensity level at a surface enveloping the
sound source
mikrofoni
lattiamaa
aumlaumlnilaumlhde
SLL IW lg10
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound propagation and attenuationSpherical wave
In a spherical
wave the sound
power of a point
source spreads
over the surface
area of a sphere
Kuva Salter et al 1999
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound propagation and attenuationSound divergence in a free field
bull Sound pressure level of a sound source at a givendistance from the source can be calculated from the sound power level (in Finnish rdquoleviaumlmisvaimennusrdquo)
where Ω is solid angle (avaruuskulma) and k is directivity factor (suuntakerroin) of the sound source
bull When Ω = 4π (spherical wave) and k = 1 we get
in a spherical wave Lp decreases 6 dB with doubling of distance
k
rLL Wp
2
lg10
11lg204lg10 2 rLrLL WWp
distance attenuation
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound propagation and attenuationEffect of location
bull The effect of location of the source (ie solid angle Ω)
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Distance attenuation in spherical wavea)
b)
c)
Spherical wave
Distance x 2 Lp - 6 dB
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Distance attenuation in cylidrical wave
Cylindrical wave
Distance x 2 Lp - 3 dB
a)
b)
c)
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound propagation and attenuationDirectivity factor
bull Definition of directivity factor k
meaning directivity factor at angle θ = sound intensity at
angle θ average intensity of sound source radiated to
all directions
bull Determining the directivity of a sound source is difficult
thus directivity information of eg HVAC equipment is
rarely available
sound sources are typically treated as point sources
(k = 1 no directivity)
kI
Ik
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound absorption
bull The sound absorption coefficient (absorptiosuhde)
describes the ability of a material to absorb sound power
bull Sound absorption coefficient α is defined as the sound
power incident on a surface W1 divided by the sound
power that is not reflected from the surface W1 ndash W2
W
W
1
2
1
21
W
WW α = 01
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Measurement of absorption coefficient
bull Absorption coefficient is a frequency-dependentquantity
bull Measured usually in one-third bands 100-5000 Hz in a reverberation chamber
(ISO 354)
bull Different single-numberdescriptors can becalculated from the measurement results (eg Absorption Class ISO 11654)
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound absorption vs sound insulation
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound absorption vs sound insulationReflection - transmission
bull Reflection
ndash Large value sound absorbed
ndash Small value sound reflected
i
ri
W
WW
i
t
W
W
α = 01
τ = 01
bull Transmission
ndash Large value most of the sound energy penetrates the structure
ndash Small value sound reflected
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound absorption vs sound insulationReflection - transmission
bull Attenuation of sound hitting a
surface as a function of
absorption coefficient
bull Attenuation of sound penetrating
the structure as a function of
transmission coefficient
1lg10D
t
i
W
WR lg10
1lg10
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Reverberation time
bull The time it takes for sound pressure level to decrease
60 dB after the sound source has been switched off
bull Measurement of reverberation time using the impulse
method
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Reverberation time
bull Reverberation time is
calculated using the
Sabine equation
bull Other formulae also
exist
A
VT 160
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Reverberation timeDiffuse sound field
bull Sabine equation assumes a diffuse sound field in the
room
bull Diffuse sound field equal sound pressure level at each
point in the room
ndash Condition is satisfied in cubic spaces with dimensions gtgt sound
wavelength and with hard sound reflecting surfaces
ndash Condition is not satisfied is the space is large and highly
absorbing or if all the absorptio material is situated on one
surface while the other surfaces are sound reflecting
bull Sabine equation can however be applied in most
spaces with sufficient accuracy
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound absorption area
bull Absorption area in Sabine equation A [m2] depends on
ndash Sound absoprtion coefficients of materials α
ndash Surface areas S of materials in the room
bull Total sound absorption area
bull Note Aabsorption area and reverberation time are
frequency-dependent quantities
i
n
1i
inn2211 SSSSA
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Examples of reverberation time
Tila Jaumllkikaiunta-aika T [s]
02 shellip03 s Aumlaumlnitarkkaamo
03 shellip08 s Elokuvateatteri
05 s Kalustettu makuuhuone
05 shellip08 s Hyvin suunniteltu luokkahuone
10 shellip12 s Teatteri suuri auditorio
15 s Kalustamaton makuuhuone
18 s Tampere-talon iso sali
2 shellip3s Suuri aula jossa ei vaimennusta
5 s Tampereen tuomiokirkko tyhjaumlnauml
95 s Helsingin rautatieasema
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound field in a room
Direct
sound
Reverberant
sound
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Room attenuation (huonevaimennus)
bull The sound pressure level produced by a sound sourcein a room can be calculated from the equation
bull The latter term is called room attenuation(huonevaimennus)
bull Equation only takes account of the sound reflected fromroom surfaces and assumes a diffuse sound field
bull Notendash A gt 4 m2
positive room attenuation (sound attenuates)
ndash A lt 4 m2 negative room attenuation (sound amplified)
4lg10
ALL wp
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Room attenuation
bull Room attenuation
4lg10
A
The absorption area
and room attenuation
of a typical furnished
room
10 m2 4 dB
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Significance of room attenuation
bull The sound level caused by a sound source depends
highly on the amount of room attenuation
must be considered eg in HVAC noise control
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound field in enclosed spaces
bull Sound pressure level in an enclosed space
Ar
kLL Wp
4lg10
2
Property of
sound source
Direct
sound
Reverberant
sound
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound field in enclosed spacesReverberation radius
bull Sound level in a room reaches a certain constant level a
few meters from the sound source
bull This distance is called reverberation radius
(kaiuntasaumlde) = the distance from the sound source at
which the level of direct and reverberant sound are
equal
4
kArk
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Sound field in enclosed spacesPuheen aumlaumlnitaso LA [dB]
20
30
40
50
60
70
80
01 1 10 100
Etaumlisyys aumlaumlnilaumlhteeseen r [m]
Diffuusi huone yhtaumllouml (420) DL2=0 dB
Avotoimisto huono vaimennus DL2=5 dB
Avotoimisto hyvauml vaimennus DL2=11 dB
Heijastukseton tila (tai ulkona)
DL2 saadaan jyrkkyydestauml
r1=2 m ja L1=53 dB
r2=4 m ja L2=42 dB
DL2=11 dB
reverberation radius
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta
Characteristics of human speech
normaali korotettu voimakas
Hz dB dB dB
250 572 615 640
500 598 656 703
1k 535 623 706
2k 488 568 659
4k 438 513 599
8k 386 426 489
A 595 665 737
Lin 626 687 747
Aumlaumlnitaso [dB]
0
20
40
60
80
250 500 1k 2k 4k 8k
Taajuus [Hz]
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
pystysuunta
Suhteellinen aumlaumlnitaso [dBA]
-10
-8
-6
-4
-2
0
2
490
80 7060
50
40
30
20
10
0
350
340
330
320
310300
290280270
260250240
230
220
210
200
190
180
170
160
150
140
130120
110100
vaakasuunta