SoundAdvisor Model 831C
C-12
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-12.
where T is Measurement Duration, T
c
is Criteria Time, L
i
is TWA, L
c
is Criteria Level, q is exchange
"Exchange Rate (Q), Exchange Rate Factor (q), Exposure Factor (k)"
Standard: ANSI S12.19
Noise Exposure
See
OSHA Level (LOSHA)
The Average Sound Level calculated in accordance with the Occupational Safety and Health
Administration Exchange Rate and Threshold Level.
Preamplifier
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.
Projected Noise Dose
Projected Noise Dose is the
Noise Dose
expected if the current rate of noise exposure continues
for the full
Criterion Duration
period.
Single Event Noise Exposure Level (SENEL, LAX)
The Single Event Noise Exposure Level is the total sound energy over a specific period. It is a spe
-
cial form of the
Sound Exposure Level
where the time period is defined as the start and end
times of a noise event such as the passing of an aircraft or automobile.
Sound
Sound is comprised of rapid oscillatory compression changes in a solid, liquid, or gas medium
that propagate to distant points. It is characterized by changes in density, pressure, motion, and
temperature. Not all rapid changes in the medium are sound since they do not propagate. Wind
noise is an example of this. Sound can also be characterized as the auditory sensation evoked by
the oscillatory changes.
Sound is the physical phenomenon associated with acoustic (small) pressure waves. Noise is
unwanted sound that causes adverse effects in those exposed to it, such as hearing loss or annoy
-
ance. It can also be defined as the sound made by other people. In every case, choosing the word
noise
involves a judgment of whether the sound is welcome or not.
Sound Exposure (E)
Sound Exposure is the total sound energy of the actual sound
during a specific time period. It is expressed in Pascals-
squared seconds, or Pascals-squared hours. The following for
-
mula describes exposure in terms of E, where p
A
is the sound
pressure and T
2
- T
1
is the Measurement Duration (specific
time period).
D
100
T
T
c
------------10
L
i
L
c
–
q
=
E
t d t
P ( )
A
2
1
2
T
T
