D-4 824 Reference Manual 9/29/09
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 and vibration.
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 unit Pascal for e.g. acoustic
measurements.
L
den
10log
10
1
24
------
10
L
i
10+10
0000
0700

10
L
i
10
0700
1900

10
L
i
5+10
1900
2200

10
L
i
10+10
2200
2400

++ +


îšîš½
=
L
dn
10Log
10
1
24
------
10
L
i
10+10
0000
0700

10
L
i
10
0700
2200

10
L
i
10+10
2200
2400

++


îšîš½
=
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