Larson Davis System 824, Руководство по обучению

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3/22/01 Environmental Measurements 2-15
Time History
From either the “Excd-a” and “Excd-b” displays, press the
Check
key to access the “Time History” display.
The Exceedance time history is triggered off of the selected
detector and uses a short Leq function to show actual energy.
PassBy Exceedance
When the parameter, “Excd Trigger”, is set to “Passby” a
special event detector is selected that measures the Lmax,
Leq, and SEL of the highest event to raise and lower 10 dB
in SPL. It is used to capture single events such as a vehicle
or aircraft passby, or other event noises such as blasts or gas
jetting noise as required by certain ordinances or standards.
In addition to the levels measured, the date and time of the
Lmax and the duration of the event are recorded.
Only events that are longer than the minimum duration and
having Lmax greater than the SPL Excd Level 1 will be
recorded.
A time history of the PassBy exceedance can be recorded by
turning on the “Excd Time-Hist”.
Passby’s
Duration
T
END
T
START
T
MAX
Lmax
10 dB