Larson Davis 831 - Community Noise Descriptors

Model 831 Manual Community Noise Descriptors C-9
Community Noise Descriptors
L
DN
The day-night level L
DN
is defined by the following
formula:
Where:
•H
D
is the number of hours programmed for "daytime",
•H
N
is the number of hours programmed for "nighttime",
• Lday is the equivalent level measured during the daytime
period,
• Lnight is the equivalent level measured during the
nighttime period
•L
PN
is the nighttime penalty level, generally 10dB.
In the default form, the day has sixteen hours (H
D
= 16) and
the night has eight hours (H
N
= 8). The defined time periods
for Day and Night times are programmed the same as L
DEN
.
Default time periods are shown below.
Generally L
DN
is 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 or night
period is assumed to represent the entire period. If there was
no measurement performed for either the day or night time
period then the number of hours used in the formula is set to
zero and the corresponding Lday or Lnight will be shown as
"- - -". The Session Log and Run Time are used to qualify
the measurement periods.




















1010
10
1010
1
log10
PN
LLnight
N
Lday
D
ND
DN
HH
HH
L