Larson Davis 831 - Page 544

Model 831 Manual Glossary D-19
The fundamental relationship between the two is logarithmic
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
pressure 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.
L
p
20log
10
p
rms
p
0
----------
= p
rms
p
0
10
L
p
20
=
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94.0dB====
Pa 20 10
6–
 10
76.3 20
 20 10
3.815 6–
 20 10
2.185–
 20 0.00650.13=====