Larson Davis System 824, Reference Manual

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A-8 824 Reference Manual 9/12/00
T is the measurement duration in hours
t is the time in hours
L is the SLOW, (or FAST) A-weighted sound level, a func-
tion of time, when the sound level is greater than or equal to
L, or equals -× when the A-weighted sound level is less than
Lt
L
t
is the threshold sound level specified by the manufacturer
L
C
is the criterion sound level specified by the manufacturer
Q is the exchange rate in dB, and q = the parameter that
determines the exchange rate, where:
q = 10 for a 3dB exchange rate
q = 5/log(2) for a 5dB exchange rate
q = 4/log(2) for a 4dB exchange rate
The factor of 100 in the equation produces a result that is a
percentage.
Dose is obtained from the accumulations made for TWA and
SEL using the formula:
where,
L
(s)
is the current SPL at sample s; for measurements that
include a threshold L(s) is set to × if L(s) is less than the
Threshold Level Lt
k is the exchange rate constant which is equal to:
10.00 for an exchange rate of 3 dB (L
eq
, or Ý 3 dB/log(2))
DOSE 10
10
L
s
( )
k
----------
s 1 =
n
∑










L
c
k
-----
T
c
115200
( )
100
( )
log + log – – log
% =