SoundAdvisor Model 831C
C-6
Eight Hour Time-Weighted Average Sound Level (L TWA(8))
It is the constant sound level that would expose a person to the same Noise Dose as the actual
(unsteady) sound levels. According to the ANSI S12.19 standard, the equation for it is
NOTE: This definition applies only for a Criterion Duration of 8 hours.
Energy Equivalent Sound Level (Leq)
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.
where p is the sound pressure and the Measurement Duration (specific time period) T=T2-T1. See
“Sound Pressure Level (SPL, Lp)” on page C-15.
Exchange Rate (Q), Exchange Rate Factor (q), Exposure Factor (k)
It is defined in ANSI S1.25 as “the change in sound level corresponding to a doubling or halving of
the duration of a sound level while a constant percentage of criterion exposure is maintained.”
The rate and the factors are given in the table below.
Standard: ANSI S12.19
Exponential Integration
The alternative to
for the 831C SLM. Exponential integration shows a long
decay of energy after an impulse. However, it may hide small events or loud impulsive events. For
this reason, this method is not as commonly used as
. Please note that when
performing time history measurements of 10 seconds or less, you must use Linear integration.
Far Field
There are two types of far fields: the acoustic far field and the geometric far field.
Acoustic Far Field
: The distance from a source of sound is greater than an acoustic wavelength. In
the far field, the effect of the type of sound source is negligible. Since the wavelength varies with
frequency (See the definition of Wavelength), the distance will vary with frequency. To be in the
far field for all frequencies measured, the lowest frequency should be chosen for determining the
L
TWA 8
L
c
qLog
10
D
100
---------
+
=
L
eq
10Log
10
p
2
t
t
d
T
1
T
2
p
o
2
T
--------------------------
=
Table C.3 Exchange Rate
Exchange Rate,
Q
Exchange Rate
Factor, q
Exposure Factor,
k
3.01
10
1
4
13.29
.75
5
16.61
.60
6.02
20
.50
Содержание 831C-FFT
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Страница 215: ...SoundAdvisor Model 831C A 51 FIGURE A 48 Model 831C with 377C20 Microphone...
Страница 216: ...SoundAdvisor Model 831C A 52 FIGURE A 49 Model 831C with 377C20 Microphone...
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Страница 218: ...SoundAdvisor Model 831C A 54 FIGURE A 52 Model 831C with 377C20 Microphone FIGURE A 53 Model 831C with 377C20 Microphone...
Страница 221: ...SoundAdvisor Model 831C A 57 FIGURE A 58 831C With LOWN Mic Set FIGURE A 59 831C With LOWN Mic Set...
Страница 222: ...SoundAdvisor Model 831C A 58 FIGURE A 60 831C With LOWN Mic Set FIGURE A 61 831C With LOWN Mic Set...
Страница 223: ...SoundAdvisor Model 831C A 59 A 10 Declaration of Conformity...
