Trane TRG-TRC007-EN manual MPa DB ref Pressure

Page 31

period two

Sound Perception and

Rating Methods

notes

Room Criteria (RC) Curves

 

80

A

 

 

 

 

 

 

 

mPa

70

B

 

 

 

 

 

 

 

60

 

 

 

 

 

 

 

 

dB ref 20

 

 

 

 

 

 

 

 

50

 

 

 

D

 

 

 

 

pressure,

40

 

 

 

 

 

 

 

RC-50

 

 

 

 

 

 

 

E

 

 

 

 

 

C

RC-45

sound

30

 

 

 

 

RC-40

20

 

 

 

 

 

 

 

RC-35

 

 

 

 

 

 

 

 

RC-30

 

 

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

RC-25

 

31.5

63

125

250

500

1,000

2,000

4,000

 

 

octave-band frequency, Hz

Figure 29

The following steps describe how to determine an RC rating.

1Plot the octave-band sound-pressure levels on the RC chart.

2Determine the SIL by calculating the arithmetic average of the sound- pressure levels in the 500 Hz, 1,000 Hz, and 2,000 Hz octave bands. In this example, the arithmetic average of 38 dB, 31 dB, and 24 dB is 31 dB.

3Draw a line (C) with a slope of –5 dB per octave that passes through the calculated SIL at the 1,000 Hz octave band. This is the reference line for evaluating the character of the sound spectrum.

4Between 31.5 Hz and 500 Hz, draw a line (D) that is 5 dB above the reference line (C). Between 1,000 Hz and 4,000 Hz, draw a second line (E) that is 3 dB above the reference line (C). These two boundary lines (D and E) represent the maximum permitted deviation to receive a neutral (N) rating.

5Judge the character of the sound quality by observing how the sound spectrum deviates from the boundary lines drawn in Step Four. Use the following criteria to choose the appropriate letter descriptor that characterizes the subjective quality of the noise.

nNeutral (N): The sound level in each of the octave bands between 31.5 Hz and 500 Hz is below line D, and the sound level in each of the octave bands between 1,000 Hz and 4,000 Hz is below line E.

nRumble (R): The sound level in any octave band between 31.5 Hz and 500 Hz is above line D.

nHiss (H): The sound level in any octave band between 1,000 Hz and 4,000 Hz is above line E.

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TRG-TRC007-EN

Image 31
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