Larson Davis 831, User Manual

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Model 831 Manual Statistical Metrics Measured 24-5
Although the six percentage values are user-defined as part
of the setup, these can be changed without resetting or
stopping a measurement, in order to display different values
of Ln.
Measurement History
When making automatic sequential measurements using the
measurement history feature, a distribution table is saved for
each measurement interval.
Spectral Statistics
When the spectral Ln mode has been enabled in the
frequency spectrum setup, the Model 831 will measure and
store spectral statistical data in addition to broadband
statistical data.
Spectral statistics are similar to broadband statistics except
that values of Ln are determined for every frequency band in
the measured spectrum. To determine spectral statistics, the
sound level in every frequency band is sampled every 100
ms. into 0.1 dB wide amplitude classes over a 199 dB span.
The resulting table, from which all values of Ln between
L
0.01
to L
99.99
can be calculated for each frequency band, is
referred to as the spectral distribution table. Both the
broadband and the spectral distribution tables are saved
whenever an overall measurement is saved. As with the
broadband distribution table, the SLM Utility-G3 software
can export the spectral distribution table from a saved
measurement to a spreadsheet which could then be utilized
to calculate any possible value of Ln for the range L
0.01
to
L
99.99
for all frequency bands
.
Measurement History
When making automatic sequential measurements using the
measurement history feature, and the spectral Ln mode has
been enabled in the frequency spectrum setup, both the
broadband and spectral distribution tables are saved for each
measurement interval.