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152 VAV-PRC011M-EN

Application Considerations

Attenuators that are simple “cups” at the plenum inlet(s) have been shown in Trane’s acoustical

mock-up to provide no measurable reduction in sound pressure in the critical octave bands which

set the occupied space noise criteria.

Certification and Testing

Terminal units should be submitted based on the same criteria. There are several ways to ensure

this by certification and testing.

Raw unit sound data can be good measurement criteria for evaluation. In using this as a basis for

comparison, the designer needs to make sure that the information is based on the AHRI Standard

880-2011 that gives the procedure for testing.

Specifying NC or RC sound levels is a possible comparison, but the designer needs to be sure the

comparison is fair. Two options are to specify the attenuation effect on which you would like the

units to be evaluated or to specify that AHRI Standard 885-2008 transfer functions be used. The

importance of AHRI Standard 885-2008 is that it is the first AHRI Standard that specifies exact

transfer functions to be used for evaluation. Previous versions of the standard gave guidelines, but

the manufacturers could choose their own set of factors.

By using NC sound levels, it is possible to express acceptable sound levels for various types of

buildings or environments. A few examples are:

Table 51. Octave band frequencies

Octave Band Center Frequency Band Edge Frequencies

125

250

500

44.6-88.5

88.5-177

177-354

354-707

1000

2000

4000

8000

707-1414

1414-2830

2830-5650

5650-11300

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