About The Ln Percentiles Page (Overall Page) - Larson Davis SoundAdvisor 831C Reference Manual

FIGURE 4-14 Overall Tab: 1/3 Octave Spectral Ln
1.
2.

4.2.6 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
User Defined
Positive Frequency Weighting
Negative Frequency Weighting
If the frequency components are too small or too large, use the Adjust Graph
function described in 4.5 Adjusting the Graph Scale.
1.
values of n.
2.
3.
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
1.
measurement. For details on this, see 6.2.2 Customizing Setup
Values On the Setup Manager Tabs.
LEARN MORE
Ln Value
"
1.
L
NF50
exceeded 60.8 dB 50% of the time during the measurement.
Understanding the Overall Tab
Ln as a function of frequency for the 6 user-selected
Ln values at highlighted band.
Frequency at highlighted band.
For a more in-depth discussion of Ln values, see
in the Appendix C Glossary.
"
= 60.8 dB means that the Fast (F) time-weighted level
1 2 3 4
A C
-A -C
4-10