Model 831 Manual Glossary D-15
spectrum).
White: It is a random sound that contains equal energy at
each frequency. In this respect, it is similar to white light.
Noise Dose (D) It is the percentage of time a person is exposed to noise that
is potentially damaging to hearing. Zero represents no
exposure and 100 or more represents complete exposure. It
is calculated by dividing the actual time of exposure by the
allowed time of exposure. The allowed time of exposure is
determined by the Criterion Duration and by the sound level
(the higher the level, the shorter the allowed time). The
sound levels must be measured with A-frequency weighting
and slow exponential time weighting. See Projected Noise
Dose.
where
T is Measurement Duration
T
c
is Criteria Time
L
i
is TWA
L
c
is Criteria Level
q is exchange rate factor; see page D-7 "Exchange Rate (Q),
Exchange Rate Factor (q), Exposure Factor (k)"
Standard: ANSI S12.19
Noise Exposure (See Sound Exposure)
OSHA Level (L
OSHA
) The Average Sound Level calculated in accordance with the
Occupational Safety and Health Administration Exchange
Rate and Threshold Level.
Preamplifier A part of the sound level meter that matches a particular
model of microphone to the meter. It must be chosen in
conjunction with a microphone and a cable that connects
them.
Projected Noise Dose It is the Noise Dose expected if the current rate of noise
exposure continues for the full Criterion Duration period.
D
100T
T
c
------------
10
L
i
L
c
–q
=
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