Casella CEL CEL-63X - Manual (Page 74)

CEL-63x Environmental & Occupational Noise Meter
74 Casella CEL
Example
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 were taken in an environment where the
noise levels vary between 50 dB and 70 dB, the sound
level would never exceed the Threshold and 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 contribute to
the L
Avg
, giving a level of approximately 40 dB, which is
much lower than the actual ambient sound levels in the
measured environment.
L
Cpk
(also L
Cpk
, L
Zpk
)
The peak C-weighted (also A-weighted or Z-weighted)
sound level.
Peak The maximum level in dB reached by the sound pressure
at any instant during a measurement period. The CEL-63x
instrument can measure the peak sound pressure using A,
C or Z weighting.
Peak is the true peak of the pressure wave, which you
should not confuse with the highest sound pressure level
(which is called L
max
).
Slow time
weighting A standard time weighting applied to measurements.
When using this setting, the instrument applies a 1 second
time constant when calculating sound pressure levels.
Slow measurements are identified by using the subscript
„S‟.
SPL The sound pressure level. This is the basic physical
measure of noise and is normally expressed in dB.
Threshold The sound pressure level below which sound
measurements are excluded from the calculation.