SoundAdvisor Model 831C
C-15
Sound Speed
The speed at which sound waves propagate. It is measured in meters per second. It should not be
confused with sound or particle velocity which relates to the physical motion of the medium itself.
Spectrum (Frequency Spectrum)
The amplitude of sound or vibration at various frequencies. It is given by a set of numbers that
describe the amplitude at each frequency or band of frequencies. It is often prefixed with a
descriptor that identifies it such as sound pressure spectrum. It is generally expressed as a spec
-
trum level.
Taktmaximal-5
An integration of the five second maximum A frequency weighted, fast time weighted sound pres
-
sure levels.
Where:
L
Amax 5s(n)
is the maximum A-weighted fast exponential time weighted sound pressure level for
each n 5-second time period and n is the number of 5 second periods accumulated during the
measurement.
Threshold Sound Level (Lt)
The A-weighted sound level below which the sound produces little or no Noise Dose accumula
-
tion and may be disregarded. It is used for hearing damage risk assessment.
Standard: ANSI S1.25
Time Weighted Average Sound Level (TWA, LTWA(TC))
It is the level of a constant sound over the Criterion Duration, that would expose a person to the
same Noise Dose as the actual (unsteady) sound over the same period. If the Exchange Rate is 3
dB then the TWA is equal to the Leq.
Where TC=T
2
-T
1
and K is the Exchange Rate Factor. It is used for hearing damage risk assessment.
Standard: ANSI S12.19
c
20.05 degC
273
+
=
m sec
c
49.03 degF
460
+
=
ft sec
n
L
n
s
AF
L
AFTM
10
5
)
(
5
max
10
log
10
L
TWA TC
K
log
10
1
T
---
10
L
p
t
K
t
d
T
1
T
2
=
