HD2010UC
- 125 -
V4.2
Sound Exposure Level:
represented by the L
E
symbol (or SEL), it is defined over a given t1 ÷ t2
time interval like:
0
10
,
2
0
2
10
T
,
log
10
dt
)
(
log
10
L
2
1
T
T
L
T
p
t
p
T
eq
t
t
E
⋅
+
=
⋅
⋅
=
∫
where:
T = t
2
-t
1
is the time interval under examination.
p
2
(t) = the square of instantaneous pressure.
p
2
0
= the square of reference pressure.
L
eq,T
= continuous equivalent sound pressure level over “T” interval
T
0
= 1s.
The level of L
E
sound exposure is expressed in decibel and can be frequency weighted. For exam-
ple, L
AE
will indicate the level of frequency weighted sound exposure with A filter.
Dose
In the field of environmental noise monitoring, preventing auditory injuries, the measurement of the
noise “Dose” is used. It is meant as a percentage fraction of a daily maximum exposure to noise:
dt
T
Q
D
T
q
L
L
c
c
∫
−
⋅
=
0
10
100
)
(
D(Q) = exposure percentage for an Exchange Rate equal to Q.
T
c
= daily exposure time (usually 8 hours).
T
= measurement time.
L
= sound pressure level when it is higher than the Threshold Level, and -
∞
otherwise.
L
c
= Criterion Level for a daily exposure corresponding to 100% of the dose.
Q
= Exchange Rate.
q
= parameter independent of the exchange rate and equal to:
•
10
for Q = 3 dB
•
5/log2 for Q = 5 dB
•
4/log2 for Q = 4 dB
Summary of Contents for DeltaOHM HD2010UC
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