Larson Davis SoundTrack LxT, User Manual

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26 Glossary and Formulas LxT Manual
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
Pa



x

s = 400 x 10 -12 Pa 2 s
T
0
= 1 s
T = t
2
- t
1
, the time interval for measurement, in seconds, for
sound exposure level and time-average sound level
SEA
The SEA parameter is used mainly in the Canadian provence
of Quebec. It is based on the theory that impulsive sounds
above 120 dBC have an effect on hearing loss which is in
addition to the that caused by non-impulsive noises. It calls
for the calculation of the parameter Leq (peak value) which
is calculated as follows:
The value of SEA is then determined as follows:
:
The formula implemented in the LxT is a simplification of
the above:
N
L
n
/10
Leq (peak value) = 10 log
10
1

10
N
n = 0
SEA = Leq (peak value) +10 log10 N
Where :
SEA = Acoustical Energy Sum
Leq (peak value) = Equivalent level of impact noises
Ln = PeakC level of the nth impact noise
N = Total number of seconds with an impact noises to which the worker is exposed
during one working day
n = number of impact noises for each level of impact noise over 120 dBC, evaluated once
per second
(impact noise below 120 dBC are not considered)
Examples of results:
SEA = 160 dB for 100 impact noises at 140 dBC
SEA = 160 dB for 200 impact noises at 137 dBC
SEA = 137,78 dB for 6 impact noises at 130 dBC