dosemeter User Manual
Page 56
Estimated Exposure
Estimates the exposure (described above) that would have been received by the wearer
if the average level measured had existed for the period defined by the criterion time.
Expressed in Pascal squared hours (Pa
2
hr).
L
AE
or SEL
The level which, if maintained constant for a period of 1 second would have the same
sound energy as that actually received by the dosemeter during the measurement
period. For example, if the measurement duration was 8 hours and the L
eq
was
85dB(A), the L
AE
would represent all of the noise energy over the 8 hour period
squashed into a duration of 1 second. L
AE
is the same as SEL (Sound Exposure Level)
Threshold
Sound Levels below the threshold are excluded from all averaging.
For example, OSHA measurements use an 80dB threshold and call for a hearing
conservation program to be implemented when the eight hour TWA exceeds 85dB (50%
dose).
Criterion Level (CL)
In dB, the normalised eight hour average weighted sound level corresponds to the
maximum permitted daily exposure or 100% noise dose.
Criterion Time (CT)
The time, in hours, used in the calculation of the % Dose and Estimated % Dose
measurement parameters. By default, this is set to 8 hours but can be configured to
other durations in the Reader unit.
Peak
The true peak level of the pressure wave (not the highest sound pressure level which is
termed the L
max
). The MODEL 22 dosemeter measures the true Peak level.
Overload
Indicated when the noise level exceeds the upper design limit of an instrument. In the
dosemeter this is set to 130dB(A) Sound Level.
Glossary
A Weighting A standard weighting of the audible frequencies designed to
reflect the response of the human ear to noise
Acoustic Calibrator An instrument that provides a reference noise source that is used
to calibrate and check the performance of a Sound Level Meter
ANSI S1.25:1991 The American (US) Standard for Personal Sound Exposure Meters
(PSEM)
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