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

period three

Acoustical Analysis

notes

Attenuation and Regeneration

return	heat pump
	(source)	supply
duct
		duct

return-air grille

diffuser

Figure 46

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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