Larson Davis SoundTrack LxT, Руководство пользователя

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LxT Manual Glossary and Formulas
C
-
5
To account for the increased impact of environmental noise
during the evening and night, penalties are added to the
measured level; 5 dB for evening and 10 dB for night, as can
be seen in the equation.
The Directive 2002/49/EC of the European Parliament and
of the Council of 25 June 2002, relating to the assessment of
environmental noise permits member states to shorten the
evening period by one or two hours and lengthen the day
and/or the night accordingly and also to choose the time for
the start of the day.
To accommodate these and other possible modifications, the
Day/Night page permits the user to modify the times for the
beginning of the Day, Evening and Night periods and the
penalties to be utilized when calculating 24-hour integrated
values.
Day-Night Average Sound
Level (DNL, L
dn
)
A rating of community noise exposure to all sources of
sound that differentiates between daytime and nighttime
noise exposure. The equation is
The continuous equivalent sound level (See definition) is
generally calculated on an hourly basis and is shown in the
equation as L.
The values for the hourly periods from midnight to 7 a.m.
have 10 added to them to represent less tolerance for noise
during sleeping hours. The same occurs from 10 p.m. to
midnight. They are energy summed and converted to an
average noise exposure rating.
Decibel (dB)
A logarithmic form of any measured physical quantity and
commonly used in the measurement of sound. Whenever the
word
level is used, this logarithmic form is implied. The
decibel provides us with the possibility of representing a
large span of signal levels in a simple manner as opposed to
using the basic pressure unit Pascal for acoustic
measurements.