Casella CEL CEL-310 - Manual (Page 42)

Appendix 1
Hours) or Pa 2 s (Pascal Squared Seconds).
In the Dose Badge system, Pa 2 h are used.
For example, a noise level of 94 dB
for 4 hours would be 1 Pa 2 x 4 hours (94 dB
= 1Pa), giving an Exposure of 4 Pa 2 h. The
8 hour period is the Criterion Time.
Fast Time Weighting
A standard time weighting applied by the
sound level measurement instrument.
IEC 61252:1993
The International Standard for Personal
Sound Exposure Meters.
Integrating Averaging Sound
Level Meter
A sound level meter which accumulates the
total sound energy over a measurement
period and calculates an average.
L AE
The A-weighted exposure level is the level
that would contain the same amount of
energy in one second as the actual noise
has during the whole measurement period.
Also see SEL
For example, if the measurement
duration was 8 hours and the L eq was 85
dB(A), the L AE would represent all of the
A-weighted noise energy for the 8 hour
period concentrated into a duration of one
second. SEL (Sound Exposure Level) is a
non-frequency weighted alternative for L
AE .
L Aeq
The A-weighted equivalent level is the level
that would contain the same amount of
energy as in the actual noise. Following the
ISO procedures, doubling the energy
results in a 3 dB change in the L
eq . This is
denoted by exchange rate Q=3.
For example, if the noise level in a
factory was a constant 85 dB and the
measurement period was 4 hours, the L
Aeq
would be 85 dB(A).
The calculation of L Aeq DOES NOT USE
a Threshold as in the calculation of L AVG .
L Aeq,t
This is the A-weighted equivalent level in
dB, measured during time period “t”.
L
AS
The A-weighted sound level measured with
Slow time weighting.
L
ASmax
The maximum A-weighted sound level
measured with Slow time weighting.
L AVG
This is a parameter used in OSHA
measurements. It is the average sound
level over the measurement period
(equivalent to L
eq ).
Normally the term is used when the
exchange rate Q is some other value than
3, such as for measurements used for the
OSHA Hearing Conservation Amendment
with Q = 5. A Threshold value is used
during the calculation of L
AVG , where any
levels below the threshold are not included.
For example, assume the threshold
level is set to 80 dB and the exchange rate
is 5 dB (Q = 5). If a one hour measurement
was taken in an environment where the
noise levels vary between 50 and 70 dB,
the sound level would never exceed the
threshold so the instrument would record
no value for the L
AVG .
However, if the sound level exceeds the
80 dB threshold for only a few seconds,
only these seconds will contribute to the
L
AVG , giving a level of around 40 dB, which
is much lower than the actual ambient
sound levels in the measured environment.
L Cpeak
The peak C-weighted sound level.
L
EP,d
This is the daily personal noise exposure
defined by ISO 1999. It is the L
Aeq,t
normalised to an 8 hour Criterion Time, i.e.
a standard day.
Page 42 - CEL-310 Dose Badge Users Handbook