Larson Davis SoundExpert LxT, User Manual

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30 Glossary and Formulas LxT Manual
16.61 for an exchange rate of 5dB (L
OSHA
)
20.00 for an exchange rate of 6dB (L
Avg
)
n is the total number of samples taken in the measurement.
The sample rate is 32 samples per second.
Time Weighting
The response speed of the detector in a sound level meter.
There are several speeds used.
Slow : The time constant is 1 second (1000 ms). This is the
slowest and is commonly used in environmental noise
measurements.
Fast : The time constant is 1/8 second (125 ms). This is a less
commonly used weighting but will detect changes in sound
level more rapidly.
Impulse : The time constant is 35ms for the rise and 1.5
seconds (1500 ms) for the decay. The reason for the double
constant is to allow the very short signal to be captured and
displayed.
Wavelength (l)
The distance between peaks of a propagating wave with a
well defined frequency. It is related to the frequency through
the following equation
where c is the sound speed and f is the frequency in Hz. It
has the dimensions of length.

c
f
--
=