11/3/00 D-19
where p
0
is the reference sound pressure of 20 µPa. The
square of the sound pressure is a power-like quantity that
can be expressed in the original form of the level definition
Sound Pressure Level can be converted to sound pressure as
follows. If the sound pressure is 1 Pascal, then the sound
pressure level is
Calibrators often use a level of 94 dB so they generate a
sound pressure of 1 Pascal.
If the sound pressure level = 76.3 dB, then the sound pres-
sure is
Energy Average (L
eq
)
: The value of a steady sound measured
over a fixed time period that has the same sound energy as
the actual time varying sound over the same period. This
descriptor is widely used. It is a fixed average (See Sound
Pressure).
Impulse
: The value of an impulsive sound. The reading will
depend on the time-weighting applied.
Unweighted Peak
: The peak value of a sound with a meter
that has flat frequency weighting and a peak detector.
Weighted Peak:
The peak value of a sound with a meter that
has a frequency weighting other than flat and a peak detec-
tor.
Sound Power(W)
The sound power emitted by a sound source. It is measured
in Watts.
L
p
10log
10
p
rms
2
p
0
2
----------
=
p
rms
2
p
0
2
10
L
p
10
⁄
=
L
p
20log
10
1
20 10
6–
•
----------------------
20log
10
50000
[]
20 4.699
[]
94.0
dB
====
Pa
20 10
6–
•
10
76.3 20
⁄
•
20 10
3.815 6–
•
20 10
2.185–
•
20 0.0065
[]
0.13=====
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