Larson Davis SoundAdvisor 831C Reference Manual page 198

Appendix C
C.1 Overview
This appendix contains technical definitions of key acoustical and vibration terms commonly used with Larson Davis instru-
ments. The reader is referred to American National Standards Institute document S1.1-1994 (R2004) for additional definitions.
Specific use of the terms defined are in the main body of the text.
C.2 Glossary of Terms
Allowed Exposure Time (T
At Lmax
Average Sound Level (L
SoundAdvisor Model 831C
Glossary
)
i
The allowed time of exposure to sound that a constant A-weighted sound level in a
chosen Criterion Level, Criterion Duration, and Exchange Rate.
The equation for T
where L is the Criterion Level, Tc is the Criterion Duration, Q is the Exchange Rate, q is
c
the Exchange Rate Factor and L
Example: If L = 90, T
c
T i = -------------------------------- -

95 90
2
This means that if a person is in this area for 2 hours and 31 minutes he will have accu-
mulated a Noise Dose of 100%.
Standard: ANSI S12.19.
See "Exchange Rate (Q), Exchange Rate Factor (q), Exposure Factor (k)"
At Lmax is one of 2 choices for the Max Spec setting on the OBA Page of the Setup
Manager. See also "Bin Max"
At L , is the instantaneous spectrum at the moment when the
max
broadband maximum occurred, such as L
)
avg
The logarithmic average of the sound during a Measurement Duration (specific time
period), using the chosen Exchange Rate Factor. Exposure to this sound level over the
period would result in the same noise dose and the actual (unsteady) sound levels. If
the Measurement Duration is the same as the Criterion Duration, then L
where the Measurement Duration (specified time period) is T=T
Exchange Rate Factor. Only sound levels above the Threshold Level are included in
the integral. Standard: ANSI S12.19
is
i
T c
T i = ---------------------------------------- - =
–
  Q 
L avg L c
2
is the Average Sound Level.
avg
= 8, Q = 3 and L = 95 then
c avg
8 8
= -------------------------------------- -
– –
 3    10 
95 90
10
T c
------------------------------------------ -
–
  q 
L avg L c
10
= 2.52 = 2 hours and 31 minutes
.
ASmax
avg
-T and q is the
2 1
=LTWA(L )
C
C-1