SoundAdvisor Model 831C
C-1
Appendix C
Glossary
T
his appendix contains technical definitions of key acoustical and vibration terms
commonly used with Larson Davis instruments. 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 this manual.
Allowed Exposure Time (T
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
i
is
where L
c
is the Criterion Level, Tc is the Criterion Duration, Q is the Exchange Rate, q is
the Exchange Rate Factor and L
avg
is the Average Sound Level.
Example: If L
c
= 90, T
c
= 8, Q = 3 and L
avg
= 95 then
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
At Lmax is one of 2 choices for the Max Spec setting on the OBA Page of the Setup
Manager. See also
At L
max
, is the instantaneous spectrum at the moment when the broadband maxi-
mum occurred, such as L
ASmax
.
Average Sound Level (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
avg
=LTWA(L
C
)
where the Measurement Duration (specified time period) is T=T
2
-T
1
and q is the
Exchange Rate Factor. Only sound levels above the Threshold Level are included in
the integral. Standard: ANSI S12.19
T
i
T
c
L
avg
L
c
–
Q
2
------------------------------------------
T
c
L
avg
L
c
–
q
10
-------------------------------------------
=
=
T
i
8
2
95
90
–
3
---------------------------------
8
10
95
90
–
10
---------------------------------------
2.52 = 2 hours and 31 minutes
=
=
=
C
Summary of Contents for 831C-FFT
Page 1: ...Larson Davis SoundAdvisor Model 831C Sound Level Meter Reference Manual...
Page 214: ...SoundAdvisor Model 831C A 50 FIGURE A 47 Model 831C with 377C20 Microphone...
Page 215: ...SoundAdvisor Model 831C A 51 FIGURE A 48 Model 831C with 377C20 Microphone...
Page 216: ...SoundAdvisor Model 831C A 52 FIGURE A 49 Model 831C with 377C20 Microphone...
Page 223: ...SoundAdvisor Model 831C A 59 A 10 Declaration of Conformity...
