Svantek SV 971A, User Manual

Page: 284 / 305

SV 971A User Manual
– Appendixes
284
APPENDIX D. DEFINITIONS AND FORMULAE OF MEASURED VALUES
D.1 B
ASIC TERMS AND DEFINITIONS
T Current time period of the measurement in seconds.
1
T
Last second of the measurement.
e
T
Exposure time in seconds (time period during which a person is exposed to the action of
noise). This parameter can be set in the
Exposure Time setup ( Measurement menu).
The available values are from 1 minute to 12 hours with 1-minute step.
h 8
T
Time period equal to 8 hours (28 800 seconds).

Exponential time constant in seconds for the giving time-weighting. Three time constants
are available:
Slow (1000 ms), Fast (125 ms), Impulse (35 ms, but on falling values a
longer time constant of 1500 ms is applied).
W Frequency-weighting filter: A , C, B or Z .
( )
t p
W
Instantaneous frequency-weighted sound pressure with the weighting filter W . Sound
pressure is expressed in pascals (Pa).
( )
t p
W

Instantaneous frequency and time-weighted
sound pressure
with the weighting filter W
and time constant

calculated from the
equation:
( ) ( )
( )

 −
  =

 − −
 
t
/ t
d e p
1
t p
2
W W
where:

– variable of integration.
( )
t r
Instantaneous sound pressure depends on
the <
RMS Integration> parameter:
( )
( )
( )



=
=

=
Exp n Integratio RMS
Lin n Integratio RMS
t p
t p
t r
W
W
0
p
Reference value (20

Pa).
( )
x log
Logarithm of x to the base 10.
Q
Exchange rate in decibels is equal to 2, 3, 4, 5 or 6. The value of Q influences the
calculations of dose meter results, namely
DOSE , D_8h and LAV . The exposure rate
equal to 3 complies with ISO R 1999 “Assessment of Occupational Noise Exposure for
Hearing
Conservation Purposes”, while Q equal to 5 complies with the American
“Occupational Safety and Health Act” – OSHA.
q
Value of q is used in the calculations of
DOSE , D_8h and LAV is taken from the
formula




=

=
3 Q 10
3 Q
2 log
Q
q
for
for