Svantek SVAN 971 - Appendix D. Definitions and Formulae of Measured Values

SVAN 971 User Manual – Appendixes
213
APPENDIX D. DEFINITIONS AND FORMULAE OF MEASURED VALUES
D.1 BASIC 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.
h8
T
Time period equal to 8 hours (28 800 seconds).

Exponential time constant in seconds for the giving time-weighting. Three time constant 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.
 
tp
W
Instantaneous frequency-weighted sound pressure with the weighting filter W. Sound
pressure is expressed in pascals (Pa).
 
tp
W
Instantaneous frequency and time-weighted
sound pressure with the weighting filter W
and time constant

calculated from the
equation:
   
 






t
/t
dep
1
tp
2
WW
where:

– variable of integration.
 
tr
Instantaneous sound pressure depends on
the <RMS Integration> parameter:
 
 
 







Exp nIntegratioRMS
Lin nIntegratioRMS
tp
tp
tr
W
W
0
p
Reference value (20 Pa).
 
xlog
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








3Q10
3Q
2log
Q
q
for
for