Larson Davis SoundAdvisor 831C Reference Manual page 207

Department of
Defense Level
(LDOD)
Dose
Detector
Eight Hour Time-
Weighted Average
Sound Level (L
TWA(8))
Energy Equivalent
Sound Level (Leq)
SoundAdvisor Model 831C
dB = 10Log
Table C.1 illustrates how a a tenfold increase of the sound pressure will result in
an increase in 20 dB steps, while sound power increases in 10 dB steps. See the
linear form (Table C.1) and compare with equation above. In conclusion, dB
values are always the same, independent of using sound power or sound
pressure as the base unit. A 6 dB increase implies four times the sound power or
two times the sound pressure.
Table C.2 Sound Power Increase
Linear form, non-squared units
Ration of Value to
Reference
1
10
100
200
1,000
10,000
100,000
1000,000
The Average Sound Level calculated in accordance with Department of Defense
Exchange Rate and Threshold Level. See Average Sound Level
"Noise Dose (D)" on page C-11
The part of a sound level meter that converts the actual fluctuating sound or
vibration signal from the microphone to one that indicates its amplitude. It first
squares the signal, then averages it in accordance with the time-weighting
characteristic, and then takes the square root. This results in an amplitude
described as rms (root-mean-square).
It is the constant sound level that would expose a person to the same Noise Dose
as the actual (unsteady) sound levels. The equation for it is
NOTE: This definition applies only for a Criterion Duration of 8 hours.
Standard: ANSI S12.19
The level of a constant sound over a specific time period that has the same sound
energy as the actual (unsteady) sound over the same period.
2
P P
------- - ----- -
= 20Log
10
2 P
P
0
0
Exponential Form of
Ratio
0
10
1
10
2
10
2.3
10
3
10
4
10
5
10
6
10
L = L + qLog
TWA 8  
c
p ; = 20Pa
0
Level form
20•Exponent
0
20
40
46
60
80
100
120
D
 
-------- -
 
10
100
C-5