Trane TRG-TRC007-EN manual Former Methods of Sound Testing

Page 67

period four

Equipment Sound Rating

notes

Former Methods of Sound Testing

I ASHRAE generic fan algorithm

I Measured fan-sound data plus prediction equations

I AMCA Standard 300

Figure 65

Historically, there have been several methods used to generate sound data for air handling equipment.

Though increasingly less common, there are still cases where fan-sound levels are based on prediction equations such as the generic fan algorithm published long ago by ASHRAE. Using this algorithm is much less costly than using an acoustic test facility, but results in much less accurate data. In 1995, after tests proved that sound levels predicted by the algorithm could vary from actual measured readings by as much as 10 dB in a given octave band, ASHRAE removed the fan prediction algorithm from the handbook, stating that:

The sound power generated by a fan performing at a given duty is best obtained from manufacturers’ test data taken under approved test conditions.

[1999 ASHRAE Handbook–Applications, Chapter 46, page 4]

Another sometimes-used rating method measures actual sound data for the fan by itself, then uses acoustical equations to predict the effects of the cabinet, coils, filters, and other components that make up the air handler. These prediction algorithms vary from manufacturer to manufacturer, and since they are usually proprietary, it is difficult to judge their accuracy. This prevents designers from effectively comparing data between manufacturers or applying that data in an analysis.

AMCA Standard 300–1996,Reverberant Room Method for Sound Testing of Fans, defines the test methodology for collecting fan-onlysound-power data. However, it has also been used to test entire air handlers. Just because the data was “taken in accordance with AMCA 300” does not indicate whether the sound data is for the fan only or for the entire air handler. This leaves the designer to determine whether the data reflects the entire air handler or, as intended, just the fan by itself.

60

TRG-TRC007-EN

Image 67
Contents Air Conditioning Clinic Fundamentals of Hvac Acoustics Business Reply Mail One of the Fundamental Series Comment CardFundamentals of Hvac Acoustics Fundamentals of Hvac Acoustics PrefaceContents TRG-TRC007-EN Fundamentals of Sound Fundamentals of SoundWhat is Sound? What is Sound?Sound Wave and Frequency Wavelength Broadband Sound and Tones Broadband SoundOctave Bands Octave BandsLogarithmic sums One-Third Octave Bands Sound Power and Sound Pressure Sound Power and Sound PressureAn Analogy Decibel DB = 10 log10 ´ log Logarithmic ScaleEquation for Sound Pressure Equation for Sound Power50 dB + 44 dB = 51 dB Logarithmic Addition of DecibelsHuman Ear Sound Perception Rating MethodsHuman Ear Response Loudness Contours Single-Number Rating Methods Response to TonesSingle-Number Rating Methods Sound Perception and Rating Methods C WeightingWeighting Example Weighting Noise Criteria NC Curves NC-39 Room Criteria RC Curves MPa DB ref Pressure Sound Perception and Rating Methods RC-31 R Phon and Sone Octave-Band Rating Method Octave-Band Rating MethodAcoustical Analysis Acoustical AnalysisSetting a Design Goal Setting a Design GoalAcoustical Analysis Source-Path-Receiver Analysis Acoustical AnalysisSource-Path-Receiver Model Airborne Typical Sound PathsExample of Multiple Sound Paths Examples of a Single Sound PathIdentifying Sound Sources and Paths Sound-Path Modeling Modeling Sound PathsSupply Algorithms for Sound-Path Modeling Computerized Analysis Tools Terms Used in Sound-Path Modeling Attenuation and RegenerationSound Transmission Insertion loss IL Noise reduction NR Transmission loss TL Absorption Reflected Sound Receiver Sound Correction Equipment Sound Rating Equipment Sound RatingFields of Measurement Free FieldDistance Correction in a Free Field = L p1 20 logLot Near Field Reverberant Field Semireverberant Field Hvac Equipment Sound Rating Rating Hvac EquipmentReverberant-Room Method Free-Field Method Industry Standards Ducted Air-Handling Equipment Air Handler Test Configurations Former Methods of Sound Testing ARI Standard Sound Power by Octave Band Review-Period One ReviewNoise criteria NC Room criteria RC Review-Period TwoReview-Period Three Review-Period Four Review Questions for Period QuizOctave-band frequency, Hz Answers Glossary Glossary Room effect See receiver room correction Glossary Trane