Climate. Master 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 Lab. VIEW 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 • Climate. Master 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
Climate. Master 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 Lab. VIEW • • Great history with Lab. VIEW for sound data measurement Lab. VIEW 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 • Climate. Master products quieter by design • Interior sound levels < NC 20
From Climate. Master to Customer • • • Sound testing as part of development ARI 260 and 350 standards Product sound data NC Climate. Master 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](https://present5.com/presentation/989803308da1f455af2a059c498a5c63/image-24.jpg "Important Definitions • Sound Power: W [watt], is a fundamental property of a sound")
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 • d. B - Decibel unit of measure expressing a log ratio of two quantities. 3 -5 d. B barely perceptible. 10 d. B 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
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 20 Hz-20 KHz • Climate. Master Sound Analyzer accommodates a wide range 50 Hz-11 KHz • 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 100 Hz, 125 Hz, and 160 Hz – Lwo = 10 log 10[Σ 10(Lw(n)/10)] • Lwo = 125 Hz 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 - 5 k. Hz – Wide range noise in occupational environment – Best with sources of wide range like music etc.
1/1 Octave Hz A-Weight Adder
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
GRH/V 030 ARI 260 Ducted Discharge Data
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
NC 50 Unit NC Rating
Climate. Master Sound Analyzer
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 Climate. Master Sound Analyzer
Thank You
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