Larson Davis System 824, Reference Manual

Page: 200 / 536

7-20 824 Reference Manual 11/8/00
Ln’s
The L
N
Centiles set the six percentile values to be measured,
logged (if selected) and shown in the Ln displays. Using
these six settings, you can select any six percentile values.
As shown above, these settings can each take on any value
within the following range:
0.00 to 99.99%
Whenever you change any percentile value, the instrument
sorts and reorders the percentile values into ascending order
as demonstrated in the following example:
Example:
Suppose you change L
n
3 from 30.0* to 5.0*. The original setting val-
ues will then be automatically sorted into ascending order and reas-
signed as shown in the table below:
Spectral Ln’s (SSA only)
The Spectral Ln setting is used to measure six Ln values for
each 1/3 octave. The setting options provided are:
Spectral Lns can be enabled as an
Overall measurement or as a func-
tion of each Interval History record. None - Spectral Ln’s are turned off.
Overall - Spectral Ln’s are computed for the over-
all measurement.
To store interval spectral Ln levels,
set “Spectral Ln” to “Interval”,
enable Ln and Interval histories and
set “Intv Save Ln” to “Yes”. Interval - Spectral Ln’s are computed for each
interval period.
NOTE: If Random Corr. is set to [Yes] and Spectral Ln is set to
[Interval] then Spectral Ln will be set to [None] and the warning
“Setting Conflict” is displayed.
Original Setting After Change and Sort
L
n
1 Percentile = 10.0 *L
n
1 Percentile = 5.0
L
n
2 Percentile = 20.0 L
n
2 Percentile = 10.0
*L
n
3 Percentile = 30.0 L
n
3 Percentile = 20.0
L
n
4 Percentile = 40.0 L
n
4 Percentile = 40.0
L
n
5 Percentile = 50.0 L
n
5 Percentile = 50.0
L
n
6 Percentile = 60.0 L
n
6 Percentile = 60.0