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Technology in ArchitectureTechnology in ArchitectureTechnology in ArchitectureTechnology in Architecture
Lecture 14
Noise Reduction by AbsorptionSound Paths
Sound Isolation
Lecture 14
Noise Reduction by AbsorptionSound Paths
Sound Isolation
Noise Reduction by Noise Reduction by AbsorptionAbsorptionNoise Reduction by Noise Reduction by AbsorptionAbsorption
Noise Reduction by Noise Reduction by AbsorptionAbsorption
Increased absorption reduces ambient noise
S: p. 761, F.18.2
Noise Reduction Noise Reduction by Absorptionby Absorption
Reverberation increases ambient sound levels
S: p. 788 F.19.1
69 db
Sound TransmissionSound Transmission
Barriers reduce sound transmission to reduce noise intrusion
S: p. 797, F.19.11
Air-Borne SoundAir-Borne Sound
Transmission Loss (TL): sound energy lost through a construction assembly
S: p. 803, F.19.17
Noise ReductionNoise Reduction
Combined effect of TL and absorption
NR=TL-10 Log (S/AR)
NR: noise reduction (db)TL: transmission loss (db)S: area of barrier wall (ft2)AR: total absorption of receiving room
(sabins, ft2)
Noise Reduction ExampleNoise Reduction Example
What is the noise reduction at 500 hz between two rooms separated by a 2x4 stud wall with ½” gyp. bd. on each side.
Receiving room absorption: 450 sabins, ft2
Separation wall: 10’ x 20’
Noise Reduction ExampleNoise Reduction Example
Find NR500
NR500=TL500-10 Log (S/AR)
=35-10 Log (200/450) =35-10 Log (0.444) =35-10(-0.35) =35+3.5=38.5 say 39db
Sound Transmission ClassSound Transmission Class
Sound Transmission Class (STC): defines overall transmission loss across center band frequencies
Barrier STC Descriptor/ ApplicationRanking
25 Poor/1 Space divider30 Fair/2 Room divider35 Very Good/4 Offices near quiet space42-45 Excellent/5 Party walls46-50 Total Privacy/6 Quiet next to noisy
from S: p. 818. T.19.6
Sound Transmission ClassSound Transmission Class
STC can be compromised by:
Combination with lesser sound barriers
Gaps in construction
“An air path is a good sound path”
Sound Transmission ClassSound Transmission Class
STC of a wall assembly
2x4 stud with gyp. Bd.
S: p.1674, Index K.1
Sound Sound Transmission Transmission ClassClass
Wall assembly description
2x4 stud with gyp. bd.
S: p. 1678, Table K.1
Sound Transmission ClassSound Transmission Class
Wall assembly selection TL data
2x4 stud with gyp. bd.
S: p. 1675, Index K.2
Sound Transmission ClassSound Transmission Class
Floor assembly follows same process
S: p. 1686, Index L.1
Noise CriteriaNoise Criteria
Noise Criteria (NC): accepted noise level for a given space.
Defined for center band frequencies
62.5 125 250 500 1000 2000 4000
Noise Criteria CurvesNoise Criteria Curves
Accepted noise level for a given space.
S: p. 749, F.17.17
Room CriteriaRoom Criteria
Room Criteria (RC(x)): accepted noise level for a given space.
Defined for NC frequencies plus extremely low frequencies
(~16 and 31.5 hz)
Beginning to replace NC curves in practice
Room Criteria CurvesRoom Criteria Curves
Room Criteria accepted noise level for a given space.
S: p. 751, F.17.18