ASHRAE - HVAC Noise and Vibration Control

8/11/2019 ASHRAE - HVAC Noise and Vibration Control

1/93

1

Industrial

Military Aviation

HVAC

OEM

Architectural

EnvironmentalMarine

ASHRAE Chapter MeetingASHRAE Chapter Meeting

HVAC Noise & Vibration ControlHVAC Noise & Vibration Control

Specifications & Best PracticesSpecifications & Best Practices

Presented By

Noise & Vibration Control, Inc.610-863-6300

www.brd-nonoise.com


2/93

2

Brief Intro to Acoustics

Specification Best Practice

Treatment Best Practices

TopicsTopics


3/93

3

Why Acoustics Matter!Why Acoustics Matter!


4/93

4

Important Acoustic Terminology

Loudness vs. Pitch

Decibels: Sound Power vs. Sound

Pressure

Decibel Weighting Networks Tonal Content


5/93

5

A 1K Hz tone at 60 dB would require a

102 dB tone at 20 Hz to sound as loud tothe human ear.


6/93

6

Common Municipal Code defines tone as:

any sound which can be distinctly heard as a single pitch or set of single pitches. and shall exist

of the one-third octave band sound pressure level in the band when the tone exceeds the arithmetic

average of the sound levels of the two contiguous one-third octave bands by five dB for frequencies

of 500 Hz and above, eight dB for frequencies between 160-400 Hz, and by 15 dB for frequencies

less than or equal to 125 Hz.

Tonal Noise


7/93

7

PWL vs. SPLSound Power vs. Sound PressureCause vs. Effect


8/93

8


9/93

9

What is the overall dBA level?

Octave Center Unweighted A-weighting A-weighted Overall

Band Frequency Sound factor (dB) Sound Resultant

Pressure (dB) Pressure (dBA) Level

1 63 94 -26 68

2 125 86 -16 70

3 250 85 -9 76

4 500 89 -3 86 91 dBA5 1,000 89 0 89

6 2,000 77 1 78

7 4,000 75 1 76

8 8,000 76 0 76

86

89

Decibel

Addition

72

86

89

79


10/93

10

(Sound Levels 270 ton Air Cooled Chiller)

-37-37-37-37-37-37-37-37-37Loss100

1008185929497999890Lw

634448555760626153Lp

A8K4K2K1K50025012563Freq (Hz)

1. Where are we now?

2. Where do we need to be?


11/93

11

13182022171410----Needed

Attenuation

502628334046526167Ordinance

634448555760626153Chiller

A8K4K2K1K50025012563Freq (Hz)

3. How much noise reduction is required?

4. What needs to be done to achieve compliance?


12/93

12

Common SpecificationStrategies

Specifications Types

Specification Best

Practices

Sub TopicsSub Topics


13/93

13

A Specification Should ProvideJust the Right Prescription

Accountability

Cost Control

Predictable Performance

Review of subjective and objective noise

criteria


14/93

14

Common SpecificationCommon SpecificationStrategiesStrategies


15/93

15

Common Spec Strategies on NoiseSensitive Projects

Specify sound data for lowest rated model asequipment basis of design

Specify all available OEM equipment low noiseoptions

Specify an equipment model that is not tonal Specify the same treatment used on the last

noise sensitive project

Retain an acoustical consultant to write thespecification

Specify base equipment and address any

noise problems at start-up


16/93

16

Published Sound Power Data

(No OEM Sound Kit Options)

OverallA-Wtd

63 125 250 500 1000 2000 4000 8000 (dBA)

1 97 94 92 97 90 88 84 82 97

2 102 103 99 99 98 94 87 84 102

3 67 70 79 83 89 91 88 80 95

4 93 99 97 100 97 91 88 80 105

Sound Power Levels (dB)Octave Band Center Frequency (Hz)

4 Different

Manufacturers &

Chiller Models

(Screw and Scroll

Designs)

Published Sound Pressure Data at 30 Away

(No OEM Sound Kit Options)Overall

A-Wtd

63 125 250 500 1000 2000 4000 8000 (dBA)1 70 67 65 70 63 61 57 55 70

2 75 76 72 72 71 67 60 57 75

3 40 43 52 56 62 64 61 53 68

4 66 72 70 73 70 64 61 53 74

Octave Band Center Frequency (Hz)

Sound Pressure Levels5(dB) @ 30'

4 Different ChillerManufacturers &

Models (Screw and

Scroll Designs)

Common Specification Strategies:

Specify sound data for lowest rated model as equipment basis of design


17/93

17

Sound Pressure Data for property line 80 away

(No OEM Sound Kit Options)Overall

A-Wtd

63 125 250 500 1000 2000 4000 8000 (dBA)

1 61 58 56 61 54 52 48 46 61

2 66 67 63 63 62 58 51 48 66

3 31 34 43 47 53 55 52 44 60

4 57 63 61 64 61 55 52 44 66


Octave Band Center Frequency (Hz)4 Different Chiller

Manufacturers &

Models (Screw

and Scroll

Designs)

Sound Pressure Data for property line 80 away(with factory OEM options)

Overall

A-Wtd

63 125 250 500 1000 2000 4000 8000 (dBA)

63 57 57 59 54 48 44 42 6052 60 61 59 56 54 46 41 62

31 33 43 46 49 51 48 42 56

57 63 61 61 60 55 52 42 64


Octave Band Center Frequency (Hz)

4 Different Chiller

Manufacturers & Models(Screw and Scroll

Designs)

None of the chillers will comply with typical nighttime

noise ordinance values of 50 to 55 dBA.


Specify sound data for lowest rated model as equipment basis of design

Specify all available OEM equipment low noise options


18/93

18

Scroll Chiller SoundPressure Levels

Z C A12

16

20

25

32

40

50

63

80

100

125

160

200

250

315

400

500

630

800

1k

1k25

1k6

2k

2k5

3k15

4k

5k

6k3

8k

10k

12k5

16k

20k Hz

30

40

50

60

70

80

90

100dB

Screw Chiller Sound

Pressure Levels


Specify an equipment model that is not tonal


19/93

19

Performance

Design

Allowance

Specification TypesSpecification Types


20/93

20

Performance Specifications

Typical performance descriptors Sound Power and/or Sound Pressure

Octave band and/or overall dB and/or dBA levels

NC or RC levels Relies on the acoustical credibility of the equipment

manufacturer May or may not have the capabilities needed

Commonly will take an exception

Spec is difficult to enforce AHRI 370, AHRI 575, AHRI 260, etc...

Spec is often not based on project target levels atreceiver positions

Performance spec may or may not address equipmentintegration issues (operating performance, maintenance,etc)


21/93

21

Performance Specification Example


22/93

22

Performance Specification Example


23/93

23

Contradictory Performance Specification

Sound attenuation solution quiet


24/93

24

Contradictory Performance Specification


25/93

25

Design Specifications = Just Right Prescription

Evaluates noise sensitive location(s) to provide

Predictable Performance

Accountability

Cost Control

Right amount of attenuation

Accounted for in the budget

Describes, provides performance, and/or

illustrates (schematic details) the materials andproducts needed


26/93

26

Design Specification

Schematic Design

Detail

ABC model JJJ


27/93

27

SchematicDesign Detail

Design

Specification

ABC solution/model


28/93

28

Loose Design Specification

ABC . . . . . . . . . . . . . . .

Result of a Loose/Generic spec

What is criteria for approving or rejecting?


29/93

29

Better Design Specification

ABC model and manufactured by ABC company or equivalent.


30/93

30

Detailed Design Specification


31/93

31

Best Design Specification

Attenuation


32/93

32

Best Design Specification Contd


33/93

33

Allowance Specifications

Equivalent advantages of pre-

purchased equipment Provides the right material that is

wanted on the project

Assures needed design will be built Levels the playing field for bidders


34/93

34

Allowance Specification

ABC Acoustic Attenuation DEF Company.


35/93

35

Specification BestSpecification BestPracticesPractices


36/93

36

Best Practices

Acoustic Design Answer 4 design questions

1. Where are we now?

2. Where do we need to be?

3. What needs to be done to get there?

4. How much will that cost?

Use 3-5 dBA safety factor Cursory review on every project, in depth review when

warranted

Assess site ambient noise levels Evaluate airborne and structure-borne transmission

System problems require system solutions


37/93

37

Best Practices

Specifications Job specific combined design/performance specs

preferred over generic performance specs

Evaluate project specific objective and subjective criteria

Indoor criteria: NC, RC, NCB, RC Mark II

Outdoor criteria: Zoning and ordinance criteria

Place in Division 15/23 with equipment

Specify single source for system acoustic performance

Specify turnkey where installation critical

Require submission for approval as orequal 10 days before bid date


38/93

38

Take Away

Location specific performance is king

and drives the design spec Design specs provide just the right

knowledge of costs that can get into

the budget Acoustic treatments/solutions need to

be in the equipment spec to ensurepredictable performance,acceptability, and accountability


39/93

39

Construction Trends

Specifications

Vibration Isolation Chiller Noise Treatments

Roof Mounted Treatments

Duct Work & Silencers

Rooftop Unit Treatments

Sub TopicsSub Topics


40/93

40

Construction Trends Less mass in building

Less space between floors Curb mounted equipment

Drop ceilings

Premium for rentable/usable space Value Engineering

Heightened sensitivity of owners

ANSI S12.60 LEED

B t P ti


41/93

41

Best Practices

Thickened slab above and

below

Floating floors

Pneumatic isolation systems

6 sided enclosures Stay away from midpoints of

column spans

Buffer from noise sensitive

spaces Source & path acoustic

treatments

Indoor Chillers


42/93

42

Source Treatments


43/93

43

Source Treatments


44/93

44

Critical Design Factors Broadband Performance

Tonal Performance

Aerodynamic Performance

Operating Efficiency Operating Costs

S ft E l P th T t t


45/93

45

Soft Enclosure Path Treatments

Hard Enclosure Path Treatments


46/93

46

Hard Enclosure Path Treatments

B t P ti


47/93

47

Best Practices

Outdoor Chillers Thickened slab for

rooftop

Evaluate loudness and

tonal content

Special consideration for

remote evap piping Evaluate building and

property line noise

Optimize aerodynamicand acoustic performance

Source and path acoustic

treatment

C S T t t


48/93

48

Compressor Source Treatments

Sound Blankets

Treat all accessible compressor circuit

components 3 to 4 lb. surface density

Fit/refit attachment features must be user

friendly

UL 764C Listed

T ti C Ci it


49/93

49

Treating Compressor Circuits

Result of generic spec


50/93

50

Result of generic spec


51/93

51

Air Intake Source Treatments


52/93

52


53/93

53

Condenser Fan Source Treatments

Acoustical plenums

Plenum with baffles

Plenum with silencer bank

Individual stack silencers

Open Plenums


54/93

54

Open Plenums

Plenum with Baffles


55/93

55

Plenum with Baffles

Plenum with Silencer Bank


56/93

56

Plenum with Silencer Bank


57/93

57

Not Recommended by OEMs

Dedicated Stack Silencers

Path Treatments


58/93

58

Wall and Fence Liners

Turnkey Acoustical Barrier Walls


59/93

59

y

20+ dBA Attenuation Systems


60/93

60

20 dBA Attenuation Systems

Best Practices


61/93

61

Integral vibration/seismic

curb

Lock down internal

isolation

Add mass inside curbs

Seal (acoustic) duct

drops

Dissipate supply breakoutnoise above deck

Plenum style acoustic

curbs

Rooftop CurbMounted AHU


62/93

62

Poor Best Practice


63/93

63

Poor Best PracticeThis is a seismic job!

In-Curb Treatment


64/93

64

Best Practices


65/93

65

RTU Configurations Increase plenum liner thickness

Utilize RTU discharge plenums on the supplyside

Avoid vane type flow modulation devices. VFD

controllers are preferred Slower fan speeds = lower noise levels

Evaluate fan wheel types. Backward inclined (BI)

and aerofoil (AF) wheels are preferred overforward curved models (FC)

Integrated Sound Attenuators


66/93

66

External


67/93

67

External

Acoustic Duct

Lagging

7 - 9 dB reduction in first 3

octave bands

Rooftop Unit Condenser Section


68/93

68

Treatments

Best Practices


69/93

69

Roof Mounted Equipment onDunnage Steel

Restrained isolators if spring UV compatible shear mounts

3 to 4 thickened slab 8 to 10 around unit

perimeter

Locate over utility space

Keep away from skylights and operablewindows


70/93

70

Cooling Towers Similar to Chiller strategies

Restrained spring isolators Condenser fan discharge

treatment

Path treatments


71/93

71

Best Practices


72/93

72

Vibration Isolation Follow ASHRAE guidelines for static deflection

Review actual deflections Isolate pipes and ducts at riser and wall

penetrations

Avoid suspended piping in mechanical roomsbelow noise sensitive space

Avoid cantilevered loads

Proper adjustment of isolator lockdowns

and snubbers


73/93

73

Acoustical Sealant

in Gap Acoustical Batt Mineral Fiber

Packing

Pipe and Duct Penetrations


74/93

74


75/93

75


76/93

76


77/93

77


78/93

78


79/93

79

Best Practices


80/93

80

Concrete inertia bases

Support elbows on base

Open springs

Seismic snubbers for

base Molded neoprene flexes

Vibration isolationhangers for 50 or entiremechanical room

Acoustic treatment rarelyneeded

Pumps

Best Practices


81/93

81

Avoid high pressure

drop models

Evaluate self

generated noise

Apply p correction

factors

Stay 3 equivalent ductdiameters away from

fittings

AHU Duct Silencers


82/93

82

Guidelines for Sound Trap PlacementNear Fans and Duct Fittings

Best Practices


83/93

83

Avoiding Respirable Fibers

Fiber free reactive duct silencers

(packless)

Media wrap of packed silencers

with spacers Closed cell thermal insulation

Open cell melamine foams


84/93

84

Best Practices


85/93

85

Duct Design

Follow ASHRAE guidelines

Follow SMACNA guidelines Control ductwork aspect ratios

Increase gauge and stiffening near units

Double wall duct

Duct shape

Target velocities consistent with targetNC goals


86/93

86

Turbulence = Regenerated Noise

Regenerated Noise at Fittings


87/93

87

Recommended maximum airflow

velocities for various installations


88/93

88

Duct

Shapes

Best Practices

R Diff


89/93

89

Select diffusers for 6 to 8NC points below roomtarget NC

Long radius 90 flexes todiffusers add 1 to 3 NCpoints

Kinked flexes add 7 to 9

NC points Balancing dampers

should be located threeequivalent duct diameters

away from diffusers andfittings

Open plenum returngrilles may require linedelbow

Room Diffusers

Best Practices

VAV B


90/93

90

VAV Boxes

Lined discharge 10 to 15

First take-off minimum 3 from discharge

Single duct VAV 1500 1700 CFM

Fan powered VAV 1100 1200 CFM External wraps for casing radiated noise

Recommended VAV Detail


91/93

91

Removable Wraps Reduce

R di t d N i


92/93

92

Radiated Noise


93/93

93

Date post:	03-Jun-2018
Category:	Documents
Upload:	mnt6176
View:	395 times
Download:	1 times

ASHRAE - HVAC Noise and Vibration Control

Documents