Larson Davis 824 - Appendix D Glossary; Average Sound Level (Lavg

9/29/09 D-1
APPENDIX
D
Glossary
This 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 for
additional definitions. Specific use of the terms defined are
in the main body of the text.
Allowed Exposure Time (T
i
) It is the allowed time of exposure to sound of a constant A-
weighted sound level given a chosen Criterion Level,
Criterion Duration, and Exchange Rate. The equation for it
is
where L
c
is the Criterion Level, T
c
is the Criterion Duration,
Q is the Exchange Rate, K is the Exchange Rate Factor and
L
avg
is the Average Sound Level.
E
xample: If L
c
= 90, T
c
= 8, Q = 3 and L
i
= 95 then
This means that if a person is in this area for 5 hours and 39
minutes he will have accumulated a Noise Dose of 100%.
Standard: ANSI S12.19
T
i
T
c
L
avg
L
c
–Q
2
-----------------------------------------
T
c
L
avg
L
c
–q
10
-----------------------------------------
==
8
10
95 90–10
-------------------------------
8
2
95 90–3
--------------------------
5.656 = 5 hours and 39 minu===