Larson Davis SoundAdvisor 831C Reference Manual page 247

Noise
Noise Dose (Dose)
Noise Exposure
OSHA Level (LOSHA)
Preamplifier
SoundAdvisor Model 831C
fore measurements made here can be used to separate the various sources of sound, but are not
useful in predicting the sound levels and sound spectrum far from the source.
Typically it is unwanted sound. This word adds the response of humans to the physical phenome-
non of sound. The descriptor should be used only when negative effects on people are known to
occur. Unfortunately, this word is used also to describe sounds with no tonal content (random):
Ambient: The all encompassing sound at a given location caused by all sources of sound. It is gen-
erally random, but need not be.
Background: The all encompassing sound at a given location caused by all sources of sound, but
the source to be measured. It is essentially the sound that interferes with a measurement.
Pink: It is a random sound that maintains constant energy per octave. Pink light is similar to pink
noise in that it has a higher level at the lower frequencies (red end of the spectrum).
White: It is a random sound that contains equal energy at each frequency. In this respect, it is sim-
ilar to white light.
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 expo-
sure 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" on page C-13.
where T is Measurement Duration, T
rate factor; "Exchange Rate (Q), Exchange Rate Factor (q), Exposure Factor (k)"
Standard: ANSI S12.19
See "Noise" on page C-12.
The Average Sound Level calculated in accordance with the Occupational Safety and Health
Administration Exchange Rate and Threshold Level.
A preamplifier is a part of a 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.
–

L i L c
100T
------------ - 10
D =
T c
is Criteria Time, L is TWA, L
c i
 q 
is Criteria Level, q is exchange
c
C-12