Appendix B
Sound Examiner SE-400 Series
35
due to a telephone ringing near the instrument, then only those seconds will contribute to the L
AVG
resulting in a level
perhaps around 40 dB (notably lower than the actual levels in the environment).
L
EQ
The true equivalent sound level measured over the run time. The term L
EQ
is functionally the same as L
AVG
except
that it is only used when the Exchange Rate is set to 3 dB and the threshold is set to none.
L
E
The sound exposure level averages the sampled sound over a one second period. Assuming the
sampled run time to be greater than one second, level exposure is the equivalent
noise that would be equal in
energy to the noise that was sampled. SEL is typically measured using a 3dB exchange rate without a threshold. (L
AE
is not used
by OSHA.)
L
Mn
Minimum SPL. Lowest SPL measured over a time interval.
L
Mx
Maximum SPL. Highest SPL measured over a time interval.
Logging
In sound studies, the saving of measurements at fixed intervals during a study, where each measurement is
determined from data processed in the previous logging interval.
L
Pk
Peak SPL. This is the highest instantaneous value obtained during a study or a session. A peak SPL measurement
is affected by the frequency response setting but not by the time response setting of the meter.
Noise
Unwanted sound.
Noise Floor
The signal magnitude at the bottom of the instrument’s linear range. Input signals below the noise floor cannot be
differentiated from the internal noise of the instrument.
L
avg
ER
log
2
2
L S E R
⁄
t
d
log
2
R TIM E
(
)
–
0
R T IM E
∫
dB
=
