3M SE, DL user manual Peak -C, Level Range dB Peak C Level Range dB

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Appendix B

PTWA

This is a projected TWA determined for a projected time (Prt) in relation to the Criterion Time (CT) as follows.

TWA = L		+ ER	log		 Prt	
	avg			2	--------	
					 CT

Peak –C

dB

The following chart illustrates the range of Sound Level with C-weighted Peak.

			Peak C Level Range
Level Range (dB)	Peak C Level Range (dB)	Level Range (dB)	(dB)
-20 to 70	42.2 to 73	20 to 110	42.7 to 113
-10 to 80	42.6 to 83	30 to 120	46.7 to 123
0 to 90	41.6 to 93	40 to 130	55.4 to 132
10 to 100	43.4 to 103	50 to 140	66.3 to 142

Preferred Noise Criterion (PNC) Curves

The Preferred Noise Criterion Curves, a type of tangency method, was an update to Beranek’s original NC curves that accounted for the lower frequency side of the criterion curves (1971). The PNC curves extended the range to 32 Hz instead of 63 Hz used in NC curves.

Projected time (Prt)

A time interval used in some calculations, usually different from the actual run time of a study or session.

Reference pressure

The sound pressure at the threshold of human hearing, as measured under standard conditions. This generally accepted magnitude of this pressure is 2 × 10-5 Pascals (Pa).

Models SE and DL