Larson Davis 831, User Manual

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C-10 Community Noise Descriptors Model 831 Manual
L
DEN
The day-evening-night level L
DEN
is defined by the
following formula:
Where:
• H
D
is the number of hours programmed for the "day"
period,
• H
E
is the number of hours programmed for "evening"
period,
• H
N
is the number of hours programmed for "night"
period,
• Lday is the equivalent level measured during the daytime
period,
• Lnight is the equivalent level measured during the
nighttime period,
• L
PE
is the evening penalty level, generally 5dB (4.7dB
for CNEL) and
• L
PN
is the nighttime penalty level, generally 10 dB.
In the default form, the day has twelve hours (H
D
= 12),
evening has four hours (H
E
= 4) and the night has eight
hours (H
N
= 8). In the default form, the day has eight hours,
the evening has four hours and the night has eight hours, as
can be seen in the equation. The default times for these
periods are as follows:
• Day: 0700 to 1900
• Evening: 1900 to 2300
• Night: 2300 to 0700
Lday, Levening and Lnight are A-weighted long-term
average sound levels measured during the day, evening and
night, respectively
Generally L
DEN
in only defined for full 24 hour periods. If
the measurement did not last for the entire 24 hours (or
more), the level measured for any partial portion of the day,
evening or night period is assumed to represent the entire
period. If there was no measurement performed for any of














     
 
 


10 10 10
10
10 10 10
1
log 10
PN PE
L Lnight
N
L Levening
E
Lday
D
N E D
DEN
H H H
H H H
L