76
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⋅
=
∫
T
0
2
0
2
0
E
dt
p
(t)
p
T
1
log
10
L
p(t):
instantaneous sound pressure
p
0
:
reference sound pressure (20
µ
Pa)
T:
duration of the measurement
T
0
:
1 second
Its relation with the equivalent continuous level is the following one:
⎟⎟
⎠
⎞
⎜⎜
⎝
⎛
⋅
−
=
0
E
t
T
t
log
10
L
L
6.2.6 Percentile levels
L
99
,
L
95
,
L
90
,
L
50
L
10
,
L
5
and
L
1
These are the levels that were exceeded during 99%, 95%, 90%, 50%, 10%,
5% and 1% of the analysis time, in decibels.
In Sound Level Meter mode they are calculated with classes of 0.1 dB using
the function
L
AF
. In the 1/1 spectrum analyser mode they are calculated with
classes of 0.5 dB and using the function
L
AT
.
In some English speaking countries, the percentile levels are known as the
exceedence levels, or the statistical levels, or simply as L
n
values, where ‘n’ is a
number from 0.1 to 99.9.
