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
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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 band
frequency of interest Hz
Minimum volume of the
test 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
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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
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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
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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
Typical Sound Pressure Levels
Sound Source
Military jet takeoff at 100 ft
Artillery fire at 10 ft
Passenger jet takeoff at 100 ft
Loud rock concert
Subway Station platform
Unmuffled large diesel engine
Computer printer room
Freight train at 100 ft
Conversational speech at 3 ft
W indow air conditioner
Quiet residential area
W hispered conversation
Buzzing insect at 3 ft
Threshold of hearing
Threshold of youthful hearing
Sound Pressure
Level
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0
Subjective
Reaction
Extreme danger
Threshold of pain
Threshold of comfort
Very loud
Moderate
Faint
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
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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
63
125
250
500
1000
2000
4000
8000
A-Weight Adder
-26.2
-16.1
-8.6
-3.2
0
1.2
1.0
-1.1
ARI 260 Test Setup Options
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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
FAN ONLY: LOW SPEED
FAN ONLY: HIGH SPEED
COOLING: LOW SPEED
COOLING: HIGH SPEED
HEATING: LOW SPEED
HEATING: HIGH SPEED
125
70
75
72
73
74
76
250
62
65
63
65
64
67
500
58
59
58
59
59
60
1000 2000 4000 8000
56
53
50
40
59
56
54
46
56
54
49
41
58
56
53
46
56
54
49
42
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
PWL, OCTAVE SOUND POWER BAND SOUND LEVEL, dB re 10-12
Watts
90
85
80
75
70
NC 70
65
60
NC 60
55
50
NC 50
45
40
NC 40
35
30
NC 30
25
20
NC 20
15
10
63
125
250
500
1000
2000
OCTAVE BAND FREQUENCY, Hz
4000
8000
Typical
NC
Curves
PWL, OCTAVE SOUND POWER BAND SOUND LEVEL, dB re 10-12
Watts
90
85
NC50
80
75
70
NC 70
65
60
NC 60
55
50
NC 50
45
40
NC 40
35
30
NC 30
25
20
NC 20
15
10
63
125
250
500
1000
2000
OCTAVE BAND FREQUENCY, Hz
4000
8000
Unit NC
Rating
ClimateMaster Sound Analyzer
Inputs Req
STEP 1
Determine Room Volume
15
ft
Width
15
ft
Height
10
ft
Room Vol
2250
ft 3
90
85
Determine distance of the occupant from the ceiling
D
STEP 3
6
ft
Determine Room/Ceiling Attenuation (CAT)
Choose Ceiling Type
Octave Band Frequency, Hz
CAT (dB)
STEP 4
63
125
250
500
1000
2000
4000
13
16
15
17
17
18
19
Determine Octave band sound power from Climatemaster data
Model
GRH006
Test type
Octave Band Frequency, Hz
125
250
500
1000 2000
63
59
57
59
55
SPL (dB)
STEP 4
4000
45
Calculate Sound Pressure
Octave Band Frequency, Hz
125
250
500
1000 2000
SPL (dB)
41.17
37.26
32.36
33.46
27.55
4000
15.65
PWL, OCTAVE SOUND POWER BAND SOUND LEVEL, dB re -12
10Watts
SPL, OCTAVE BAND SOUND PRESSURE lEVEL, dB re .0002 MICROBAR
STEP 2
Length
NC CURVE
80
75
70
65
60
55
50
45
40
35
30
25
20
15
-ve values may
be assumed as 0
10
63
STEP 5
125
Verify NC acceptable Levels
Very Quiet
NC 15
NC 25
Moderate
NC 35
NC 45
250
500
1000
2000
OCTAVE BAND FREQUENCY, Hz
Very Noisy
NC 55
NC 65
Extremely Noisy
NC 75+
NC 15
NC 20
NC 25
NC 30
NC 40
NC 45
NC 50
NC 55
NC 65
NC 70
Simulated
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