Trane TRG-TRC007-EN manual Review-Period Two, Noise criteria NC Room criteria RC

Page 71

period five

Review

notes

Review—Period Two

I A-weighting

 

80

 

 

 

 

 

 

 

mPa

 

 

 

 

 

 

RC

70

 

 

 

 

 

 

 

 

 

 

 

 

K Outdoor environments

 

 

 

 

 

 

chart

 

 

 

 

 

 

 

and hearing protection

20

60

 

 

 

 

 

 

 

 

 

 

 

 

 

 

dB ref

 

 

 

 

 

 

 

I Noise criteria (NC)

50

 

 

 

 

 

 

 

I Room criteria (RC)

pressure,

30

 

 

 

 

 

 

 

K Indoor environments

 

40

 

 

 

 

 

 

50

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

45

K Indoor environments

sound

20

 

 

 

 

 

 

40

 

 

 

 

 

 

35

 

 

 

 

 

 

 

 

 

K Also describes sound

 

 

 

 

 

 

 

 

30

 

 

 

 

 

 

 

 

25

character

 

10

 

63

125

250

500

1,000 2,000 4,000

 

31.5

I Octave-band data

 

 

octave-band frequency, Hz

Figure 70

Period Two discussed how the human ear perceives sound. As a selective sensory organ, the human ear is more sensitive to high frequencies than to low frequencies. The sensitivity of the human ear at a particular frequency also changes with loudness.

Many single-number rating systems have been developed over the years and each has its advantages and drawbacks. This clinic focused on some of the more commonly used rating systems, including A-weighting, Noise Criteria (NC), and Room Criteria (RC). A-weighting is typically used to describe the sound in outdoor environments, and for determining whether or not hearing protection is required in certain industrial environments. Noise Criteria and Room Criteria are used to describe the sound in indoor environments. The RC method has the added feature of describing the character, or quality, of the sound, as well as its loudness. However, because most HVAC equipment manufacturers do not have sound-power data for the 16 Hz and 31.5 Hz octave bands, it is difficult to predict the sound-pressure levels in these octave bands.

Finally, both sound-power levels and sound-pressure levels can be described using either full or one-third octave bands. Octave-band sound-power data is commonly used for describing the sound generated by HVAC equipment. It can also be used to describe the sound in either indoor or outdoor environments.

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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 Response Sound Perception Rating MethodsHuman Ear 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
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