Larson Davis 831C-FFT, Справочное руководство

Страница: 251 / 254

SoundAdvisor Model 831C C-16
Weighted Peak
: The peak value of a sound with a meter that has a frequency weighting other
than flat and a peak detector.
Sound Power (W)
The sound power emitted by a sound source. It is measured in Watts.
Sound Power Level (PWL, Lw)
The logarithmic form of sound power. It is also expressed by attachment of the word decibel to
the number. The logarithm is taken of the ratio of the actual sound power to a reference sound
power, which is 1 pico-watt. Sound power level cannot be measured directly, but can only be
deduced through measurements of sound intensity or sound pressure around the source. The
equation for it is
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
pressure 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.
L
w
10log
10
W
W
0
--------
= W W
0
10
L
w
10

=
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