Trane TRG-TRC007-EN manual MPa DB ref Pressure

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.

24 TRG-TRC007-EN