Larson Davis SoundAdvisor 831C Reference Manual page 213

Time Weighting
Vibration
Wavelength (l)
Wavenumber (k)
SoundAdvisor Model 831C
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 envi-
ronmental 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 rea-
son for the double constant is to allow the very short signal to be captured and displayed.
The oscillatory movement of a mechanical system (generally taken to be solid). It is used as a
broad descriptor of oscillations.
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.
A number that is related to the wavelength of sound and is used to compare the size of objects rel-
ative to the wavelength or the time delay in sound propagation. It is related to wavelength
through the following equation
where l is the wavelength, c is the sound speed, f is the frequency in Hz, and w is the radian fre-
quency. It has the dimensions of inverse length.
c

= - -
f

2 2f
k = ----- - = ------- - = --- -

c c
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