Casella CEL CEL-62X User Manual
Page 30
Casella CEL Limited
30
included. For example, assume the threshold level is set to 80dB and the exchange
rate is 5dB (Q = 5). If a one hour measurement was taken in an environment where
the noise levels vary between 50 and 70dB, the sound level would never exceed the
Threshold so the instrument would record no value for the LAVG. However, if the
sound level exceeds the 80dB Threshold for only a few seconds, only these seconds
will contribute to the LAVG, giving a level of around 40dB, which is much lower than
the actual ambient sound levels in the measured environment.
L
Cpeak
The peak C-weighted sound level.
L
EP,d
(L
EX,8h
)
This is the daily personal noise exposure defined by ISO 1999. It is the LAeq
normalised to an 8 hour Criterion Time, i.e. a standard day. Assuming the noise level
for the rest of the 8 hour reference period is “quiet”, the LEP,d will be: lower than the
Leq when the measurement duration is less than 8 hours, equal to the Leq for a
measurement of 8 hours, higher than the Leq for measurements longer than 8 hours.
For example, if a noise measurement was made for 4 hours and the LAeq value was
90dB(A), the LEP,d value would be calculated to be 87dB(A) as the measurement
duration is half the 8 hour Criterion Time and the exchange rate is 3 dB.
L
Ceq
The C-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.
PEAK
The maximum level in dB reached by the sound pressure at any instant during a
measurement period. With the CEL-62X, peak is measured with either C, Z or A
weighting. It is the true peak level of the pressure wave, which should not be
confused with the highest sound pressure level, termed Lmax.
SLOW TIME WEIGHTING
A standard time weighting applied by the noise measurement instrument.
SPL
The sound pressure level. This is the basic physical measure of noise, and is
normally expressed in dB.
THRESHOLD
A threshold level below which sound is excluded from calculation. OSHA
measurements use an 80 dB threshold.