Trane TRG-TRC007-EN manual Attenuation and Regeneration, Terms Used in Sound-Path Modeling

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period three

Acoustical Analysis

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Attenuation and Regeneration

return	heat pump
return	(source)	supply
duct		supply
		duct

return-air grille

diffuser

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Terms Used in Sound-Path Modeling

This section introduces several terms that are fairly specific to the science of acoustics.

Attenuation refers to the reduction in sound level as sound travels along the path from a source to a receiver. It is typically used to refer to the reduction of sound as it travels through a duct system. Straight ducts, elbows, junctions, and silencers are examples of elements that attenuate sound.

Regenerated sound results from components of the duct system that create turbulence in the air stream. Turbulence is caused by an abrupt change in airflow direction or velocity with a corresponding static-pressure loss. Regenerated sound increases with air velocity or when the air is forced to make sharp turns. Elbows, junctions, diffusers, silencers, and dampers are all examples of elements that regenerate sound.

Notice that some elements can both attenuate and regenerate sound. For example, as air makes a 90-degree turn in a rectangular duct elbow, some of the sound is reflected back upstream, attenuating the airborne sound downstream of the elbow. At the same time, however, the turbulence created by the air turning the sharp corner causes some regenerated sound.

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Contents Air Conditioning Clinic Fundamentals of Hvac Acoustics Business Reply Mail Comment Card One of the Fundamental SeriesFundamentals of Hvac Acoustics Preface Fundamentals of Hvac AcousticsContents TRG-TRC007-EN Fundamentals of Sound Fundamentals of SoundWhat is Sound? What is Sound?Sound Wave and Frequency Wavelength Broadband Sound Broadband Sound and TonesOctave Bands Octave BandsLogarithmic sums One-Third Octave Bands Sound Power and Sound Pressure Sound Power and Sound PressureAn Analogy DB = 10 log DecibelLogarithmic Scale 10 ´ logEquation for Sound Power Equation for Sound PressureLogarithmic Addition of Decibels 50 dB + 44 dB = 51 dBSound Perception Rating Methods Human EarHuman Ear Response Loudness Contours Response to Tones Single-Number Rating MethodsSingle-Number Rating Methods C Weighting Sound Perception and Rating MethodsWeighting 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 Acoustical Analysis Source-Path-Receiver AnalysisSource-Path-Receiver Model Typical Sound Paths AirborneExamples of a Single Sound Path Example of Multiple Sound PathsIdentifying Sound Sources and Paths Modeling Sound Paths Sound-Path ModelingSupply Algorithms for Sound-Path Modeling Computerized Analysis Tools Attenuation and Regeneration Terms Used in Sound-Path ModelingSound Transmission Insertion loss IL Noise reduction NR Transmission loss TL Absorption Reflected Sound Receiver Sound Correction Equipment Sound Rating Equipment Sound RatingFree Field Fields of Measurement= L p1 20 log Distance Correction in a Free FieldLot Near Field Reverberant Field Semireverberant Field Rating Hvac Equipment Hvac Equipment Sound RatingReverberant-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 Review-Period OneReview-Period Two Noise criteria NC Room criteria RCReview-Period Three Review-Period Four Review Quiz Questions for PeriodOctave-band frequency, Hz Answers Glossary Glossary Room effect See receiver room correction Glossary Trane