Larson Davis SoundAdvisor 831C Reference Manual page 45

FIGURE 4-14
Overall Tab: 1/3 Octave Spectral Ln
1.
2.
About the Ln Percentiles Page (Overall Page)
FIGURE 4-15
SoundAdvisor Model 831C
The normalized octave band page displays the numerical values of the highlighted band.
The data is then normalized using the Spectral Ln value you select in the measurement
setup file.
Table 4.3 Reference Spectra Options
Positive Frequency Weighting
Negative Frequency Weighting
If the frequency components are too small or too large to view in the graph, press Menu (
*/
) Adjust Graph. The Buffer Overrun line item is an indication that rarely displays when
using the 831C in FFT Mode while sampling sound at higher frequency resolutions. It indicates
that some samples may have been lost.
1.
User Defined
1.
Ln as a function of frequency for the 6 user-selected
values of n.
2.
Ln values at the intersection of the highlighted band.
3.
Frequency at highlighted band.
3.
An Ln percentile is a statistical measurement of the level that
exceeds the selected value "n" percent of the time. The
statistics are based on the level defined by the current
weighting and detector.
The Ln Percentiles page displays the 6 Ln statistics for the
measurement based on the run time, and the maximum and
minimum sound levels measured. You can customize the
threshold level in the measurement setup prior to or during a
measurement. For details on this, see 6.2.2 Customizing Setup
Values On the Setup Manager Tabs.
For a more in-depth discussion of Ln values, see
LEARN MORE
Ln Value in the Appendix C
" "
1.
L = 60.8 dB means that the Fast (F) time-weighted level
NF50
exceeded 60.8 dB 50% of the time during the measurement.
SoundAdvisor 831C Display In SLM Mode
1 2 3 4
A C
-A -C
Glossary.
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