Larson Davis System 824, Руководство по обучению

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3/22/01 Environmental Measurements 2-19
DNL (L
dn
)
The DNL (Day-Night Average Sound Level) is the equiva-
lent sound level for the entire measurement period with a
+10 dB weighting applied to all sounds occurring between
the time of 10:00 PM to 7:00 AM.
CNEL
CNEL is similar to L
dn
except that 5 dB is added to the mea-
surement levels between 7:00 PM and 10:00 PM and 10 dB
are added between 10:00 PM to 7:00 AM.
These measurements are used because people tend to be
more sensitive to noise during the nighttime and early morn-
ing hours.
Background Leq
Background Leq can be considered
the Leq expected if the exceedances
had not occurred. The Background Leq is the total energy minus the total
energy (event Leq) of any valid event during the entire mea-
surement period.
Excd Leq
The Excd Leq is the total energy for all exceedances that
occurred the entire measurement period or run time of the
824.
Use the
arrow keys to step
between the two Metrics displays.