ClimateMaster Engineering Sound Lab By Wes Wostal.

ClimateMaster Engineering Sound Lab

By Wes Wostal

How The New Sound Lab Evolved

• Importance of sound • Great products... No real way to design for

sound• Easy justification

Design Goals

• Must be in house• Test capability to 50 & 60 Hz• Construction of reverberant room• Construction of “ducted discharge” room• National Instruments LabVIEW• ISO 3741• NAVLAP certified• Capable of taking us into the future

In House Lab

• Outside sound testing is expensive• Outside testing offers little to no design

change opportunity

Test Capability Down to 50 & 60 Hz

• Wave length: λ = c/f

• Wave length at 60 Hz = 18.8 ft• Wave length at 125 Hz = 9.0 ft

• ClimateMaster sound lab internal dimensions: 31’L x 24’ W x 19’ T

• c (air) = 1128 ft/sec • f = frequency (Hz)

Reverberant Room Size Requirements Chamber Volume by ISO 3741

Lowest 1/3 octave bandfrequency of interest Hz

Minimum volume of thetest room m³

100 Hz 200 m³

125 Hz 150 m³

160 Hz 100 m³

200 Hz and higher 70 m³

ClimateMaster Reverberant Room Volume

400 m³

=

14136 ft³

Construction Reverberant Room

• Isolated slab• 4” thick inner steel walls• 8” thick outer sand filled concrete block wall• 1’ wide air gap• 2’ effective wall thickness• Sound attenuators for return and supply air

Construction “Ducted Discharge” Room

• 4” thick perforated steel walls • Single sound attenuator for return and supply

Air

National Instruments LabVIEW

• Great history with LabVIEW• LabVIEW for sound data measurement• LabVIEW for room conditioning• 25 tons of air side conditioning• 30 tons of water side conditioning• 10,000 CFM variable frequency drive air handler• 36” double walled duct

ISO 3741

• Acoustics - Determination of sound power levels of noise sources using sound pressure - Precision methods for reverberation rooms

• Specifies room requirements, source location, general rules for operating conditions, instrumentation and techniques for obtaining sound pressure levels from which sound power levels are calculated with grade 1 accuracy

NAVLAP Certified

• National Voluntary Laboratory Accreditation Program

• Administered through NIST

Capable Of Taking Us Into The Future

• ClimateMaster products quieter by design• Interior sound levels < NC20

From ClimateMaster to Customer

• Sound testing as part of development• ARI 260 and 350 standards• Product sound data• NC• ClimateMaster Sound Analyzer

ARI 260

Sound Rating of Ducted Air Moving and Conditioning Equipment

Adopted in 2000

Revised in 2001

What is ARI 260?

• Sound rating standard for ducted air moving and conditioning equipment

• Establishes a method of sound rating indoor a/c equipment

• Covers air source-ARI 240, & 340; water source-ISO 13256; fan Coil-ARI 440; central station ARI 430

• Provides for standard published data

Why ARI 260?

• Previously no valid sound rating standard for wshp’s

• Every manufacturer used different testing procedure

• Sound rating comparisons between manufacturers were impossible

Important Definitions• Sound Power: W [watt], is a fundamental

property of a sound source, the amount of acoustic energy radiated into the environment. denoted by ‘Lw’

• Sound Pressure: is the expression of the acoustic power in the environment. denoted by ‘Lp’

• Reference Sound Source: A portable, aerodynamic sound source that produces a known stable broad band sound power output.

Sound Power Vs Pressure

Definitions Continued• Comparison Method: A method of determining sound

power level of a source under test in a reverberation room by comparing the average sound pressure level of that source to the average sound pressure level of a reference sound source of know sound power level output. the difference in sound power level is equal to the difference in sound pressure level when the conditions in the room are the same for both sets of measurements.

Definitions Continued

• Frequency or Hz - Cycles per second• Frequency Spectrum - Audible range of

frequency 20 - 20000 Hz for humans• dB - Decibel unit of measure expressing a log

ratio of two quantities. 3-5dB barely perceptible. 10dB is perceived as twice as loud

Definitions Continued

• Octave Band: a band of sound covering a range of frequencies such that the highest is twice the lowest. octave band frequencies are: 63; 125; 250; 500; 1000; 2000; 4000; and 8000

• 1/3 Octave Band: A band of sound covering a range of frequencies such that the highest frequency is the cube root of two times the lowest. 1/3 octave band frequencies for the 125 Hz octave band are: 100; 125; and 160.

What is Sound

• A disturbance that propagates in an elastic medium (air)

• Created by a transference of mechanical energy to the medium

• Generally associated with the auditory sensation created by the disturbance in the medium

What is Noise?

• Unwanted Sound: A waste byproduct of mechanical, electrical, and fluid processes

• Noise consists of energy at frequencies that are representative of the mechanical processes that create the sound

Frequency Spectrum

Vibration

Fan, Comp and Pump Noise

Terminal Boxes

Transformer and Ballasts

Recip and Centrif Chillers

Damper Noise

Diffuser Noise

16 32 63 125 250 500 1k 2k 4k 8k 16k

Octave Band Center Frequency

Throb Rumble Roar Whistle Hiss

Typical Sound Pressure LevelsSound Source

Sound Pressure Level

Subjective Reaction

Military jet takeoff at 100 ft 140 Extreme danger

Artillery fire at 10 ft 130Passenger jet takeoff at 100 ft 120 Threshold of pain

Loud rock concert 110 Threshold of comfort

Subway Station platform 100Unmuffled large diesel engine 90 Very loud

Computer printer room 80Freight train at 100 ft 70Conversational speech at 3 ft 60Window air conditioner 50 Moderate

Quiet residential area 40Whispered conversation 30Buzzing insect at 3 ft 20Threshold of hearing 10 Faint

Threshold of youthful hearing 0 Threshold of hearing

Why is Measuring Sound So Difficult?• Measuring sound is more difficult than pressure or

temperature• Requires detailed analysis of distinct frequencies• Human ears sense sound from 20Hz-20KHz• ClimateMaster Sound Analyzer accommodates a

wide range 50Hz-11KHz• More than 10,000 data points to analyze per test

• We have the solution!!

Product Sound Data

• Product Sound Test Method– Set room conditions– Run ambient / background test– Run RSS (reference sound source)– Run test unit

Product Sound Data

• Sound Data Collected– Sound pressure of ambient – Sound pressure of RSS– Sound pressure (Lp) of unit

Product Sound Data

• 1/3 octave sound power calculations

– Sound power: Lw = Lp + (Lwp - Lpr)• Lp = Sound pressure of unit• Lwp = Sound power of the RSS• Lpr = Sound pressure of the RSS

Product Sound Data

• 1/1 octave sound power calculations• Example 100Hz, 125Hz, and 160Hz

– Lwo = 10log10[Σ10(Lw(n)/10)]• Lwo = 125Hz octave band sound power• Lw(n) = sound power of each 1/3 octave

• Lwo = 1/1 octave sound power = published data

A & C Weighted Sound Power Level

• A Weighted Sound Power Level– Range of 700 - 4000 Hz– Noise in occupational environment– Best with sources of similar range

• C Weighted Sound Power Level– Range of 50 - 5kHz– Wide range noise in occupational environment– Best with sources of wide range like music etc.

1/1 Octave Hz A-Weight Adder

63 -26.2

125 -16.1

250 -8.6

500 -3.2

1000 0

2000 1.2

4000 1.0

8000 -1.1

ARI 260 Test Setup Options

• Ducted discharge• Ducted inlet• Free inlet and casing radiated• Casing radiated• Free inlet

Ducted Discharge

Ducted Inlet

Free Inlet & Casing Radiated

Casing Radiated

Free Inlet

GRH/V 030 ARI 260 Free Inlet & Case Radiated Data

OCTAVE BAND FREQUENCY, Hz

MODE 125 250 500 1000 2000 4000 8000FAN ONLY: LOW SPEED 70 62 58 56 53 50 40

FAN ONLY: HIGH SPEED 75 65 59 59 56 54 46COOLING: LOW SPEED 72 63 58 56 54 49 41COOLING: HIGH SPEED 73 65 59 58 56 53 46HEATING: LOW SPEED 74 64 59 56 54 49 42HEATING: HIGH SPEED 76 67 60 59 56 53 47

GRH/V 030 ARI 260 Ducted Discharge Data

OCTAVE BAND FREQUENCY, Hz

MODE 125 250 500 1000 2000 4000 8000

FAN ONLY: LOW SPEED 77 65 68 64 62 62 57

FAN ONLY: HIGH SPEED 72 68 69 69 66 65 61

COOLING: LOW SPEED 82 65 68 65 63 63 57

COOLING: HIGH SPEED 80 66 68 66 64 63 58

HEATING: LOW SPEED 84 67 69 65 63 62 58

HEATING: HIGH SPEED 83 67 69 67 64 63 59

NC (Noise Criterion Curves)

• Provide a coloration curve of response that represents the ear’s sensitivity to sound

• Curve range is 63 - 8000 Hz and on an octave band sound pressure scale

• Often used in building design• Source sound pressure level measured at

each octave band must be below the specified NC curve to meet NC rating

Typical NC

Curves

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

63 125 250 500 1000 2000 4000 8000

OCTAVE BAND FREQUENCY, Hz

PW

L,

OC

TAV

E S

OU

ND

PO

WE

R B

AN

D S

OU

ND

LE

VE

L,

dB

re

10

-12

W

att

s

NC 70

NC 60

NC 50

NC 40

NC 30

NC 20

Unit NC Rating

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

63 125 250 500 1000 2000 4000 8000

OCTAVE BAND FREQUENCY, Hz

PW

L,

OC

TAV

E S

OU

ND

PO

WE

R B

AN

D S

OU

ND

LE

VE

L,

dB

re

10

-12

W

att

s

NC 70

NC 60

NC 50

NC 40

NC 30

NC 20

NC50

ClimateMaster Sound Analyzer

Inputs Req

STEP 1 Determine Room VolumeLength 15 ft

Width 15 ft

Height 10 ft

Room Vol 2250 ft3

STEP 2 Determine distance of the occupant from the ceilingD 6 ft

STEP 3 Determine Room/Ceiling Attenuation (CAT)

63 125 250 500 1000 2000 4000

CAT (dB) 13 16 15 17 17 18 19

STEP 4 Determine Octave band sound power from Climatemaster data Model

Test type

125 250 500 1000 2000 4000SPL (dB) 63 59 57 59 55 45

STEP 4 Calculate Sound Pressure

125 250 500 1000 2000 4000

SPL (dB) 41.17 37.26 32.36 33.46 27.55 15.65

STEP 5 Verify NC acceptable Levels

Octave Band Frequency, Hz

GRH006

Octave Band Frequency, Hz

Choose Ceiling Type

Octave Band Frequency, Hz

NC CURVE

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

63 125 250 500 1000 2000 4000 8000

OCTAVE BAND FREQUENCY, Hz

PW

L, O

CT

AV

E S

OU

ND

PO

WE

R B

AN

D S

OU

ND

LE

VE

L, d

B r

e 1

0-1

2 W

att

s

SP

L, O

CT

AV

E B

AN

D S

OU

ND

PR

ES

SU

RE

lE

VE

L, d

B r

e .0002 M

ICR

OB

AR

NC 15 NC 20 NC 25 NC 30 NC 35

NC 40 NC 45 NC 50 NC 55 NC 60

NC 65 NC 70 Simulated

NC 70

NC-60

NC 50

NC 40

NC30

NC 20

Glass Fiber 0.1 lb/ ft2 Density 5/8 in Thick

Ducted Discharge

NC 15 NC 25 NC 35 NC 45 NC 55 NC 65 NC 75+

Very Quiet Moderate Very Noisy Extremely Noisy

-ve values may be assumed as 0

Important Notes

• 63 Hz is difficult to test• 125 Hz is most problematic octave

About Comparison

• Must be ‘apples to apples’-Look for ARI 260 conformance

• Look for weighting ‘A’ versus ‘C’• No ARI 260... No comparison

Things to Remember• Sound power is pure source energy• Sound pressure is source with room affects• Sound power can be used to predict sound

pressure in a specified room• ARI 260 and 350 are THE ONLY sound

rating standards• Comparisons valid using ARI 260 only• Use the ClimateMaster Sound Analyzer

Thank You