Spider DSA User’s Manual
239
◼ Slow uses a time constant of 1,000 ms. Slow averaging is useful for
tracking the sound pressure levels of signals with sound pressure
levels that vary slowly.
◼ Fast uses a time constant of 125 ms. Fast averaging is useful for
tracking the sound pressure of signals with sound pressure levels that
vary quickly.
◼ Impulse uses a time constant of 35 ms if the signal is rising and
1,500 ms if the signal is falling. Impulse averaging is useful for
tracking and recording sudden increases in the sound pressure level.
◼ User Defined allows you to specify a time constant suitable for your
particular application.
Time-weighted sound level (in dB) is twenty times the logarithm to the base
ten of the ratio of a given RMS sound pressure to the reference sound pressure,
RMS sound pressure is obtained with standard time and frequency weighting.
(Example letter symbols are L
AF
, L
AS
, L
CF
, L
CS
)
Maximum and minimum time-weighted sound level (in dB) is the
greatest and lowest time-weighted sound level within a stated time interval.
(Example letter symbols are L
AFmax
, L
ASmax
, L
CFmax
, L
CSmax
, L
AFmin
, L
ASmin
, L
CFmin
, L
CSmin
)
Time-average sound level (equivalent continuous sound level) (in dB)
is twenty times the logarithm to the base ten of the ratio of a RMS sound pressure
during a stated time interval to the reference sound pressure, sound pressure
being obtained with a standard frequency weighting. (Example letter symbols are
L
Aeq
, L
Ceq
)
Sound exposure is the time integral of the square of sound pressure over a
stated time interval or event. Sound exposure is used to measure high-level, short
duration noises and to study their effects on humans.
Sound exposure level (in dB) is the total sound energy of a single sound
event that takes into accounts both its intensity and duration. Sound exposure
level is the sound level you would experience if all of the sound energy of a sound
event occurred in one second. Normalization to duration of one second allows for
the direct comparison of sounds of different durations.
Figure 148. Sound exposure level illustration.
To Next Page
Loading...