Casella CEL CEL-62X - Manual (Page 29)

8. APPENDIX A
GLOSSARY OF TERMS
This Appendix gives a glossary of the acoustic terminology used in this manual. For
further information, please contact Casella CEL or your local representative.
A, C and Z WEIGHTING (WEIGHTED)
A standard weighting of the audible frequencies designed to approximate the
response of the human ear to noise.
ACOUSTIC CALIBRATOR
An instrument that provides a reference noise source with a standard level and
frequency used to calibrate and check the performance of sound level meters and
noise dosimeters.
Decibel (dB)
The standard physical unit for measuring sound level and noise exposure.
dB(A)
A-weighted sound level in decibels.
dB(C)
C-weighted sound level in decibels.
dB(Z)
Z-weighted sound level in decibels.
FAST TIME WEIGHTING
A standard time weighting applied by the sound level measurement instrument.
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.
L
Aeq
The A-weighted equivalent level is the level that would contain the same amount of
noise energy as in the actual noise, effectively giving an average level over the
measurement period. Following the ISO procedures, doubling the energy results in a
3dB change in the Leq. This is denoted by exchange rate Q=3. For example, if the
noise level in a factory was a constant 85dB and the measurement period was 4
hours, the LAeq would be 85dB(A). The calculation of LAeq does not use a threshold
as in the calculation of LAVG, except for the LAEQ (T80) parameter defined for the
ACGIH standard.
L
AF
The A-weighted sound level measured with Fast time weighting.
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 Leq). Normally the term is used when the
exchange rate Q is some value other 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 LAVG, where any levels below the threshold are not
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