**Sound exposure** is the integral, over time, of squared sound pressure. The SI unit of sound exposure is the pascal squared second (Pa^{2}·s).

Sound exposure, denoted *E*, is defined by

E
=
∫
t
0
t
1
p
(
t
)
2
d
t
,
where

the exposure is being calculated for the time interval between times *t*_{0} and *t*_{1};
*p(t)* is the sound pressure at time *t*, usually A-weighted for sound in air.
**Sound exposure level** (SEL) or **acoustic exposure level** is a logarithmic measure of the sound exposure of a sound relative to a reference value.

Sound exposure level, denoted *L*_{E} and measured in dB, is defined by

L
E
=
1
2
ln
(
E
E
0
)
N
p
=
log
10
(
E
E
0
)
B
=
10
log
10
(
E
E
0
)
d
B
,
where

*E* is the sound exposure;
*E*_{0} is the reference sound exposure;
1 Np = 1 is the neper;
1 B = 1/2 ln 10 is the bel;
1 dB = 1/20 ln 10 is the decibel.
The commonly used reference sound exposure in air is

E
0
=
400
μ
P
a
2
⋅
s
.
The proper notations for sound exposure level using this reference are *L*_{W/(400 μPa2⋅s)} or *L*_{W} (re 400 μPa^{2}⋅s), but the notations dB SEL, dB(SEL), dBSEL, or dB_{SEL} are very common, even if they are not accepted by the SI.