Larson Davis System 824, Technical Reference Manual

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G-4 824 Reference Manual 9/29/09
Question #4
What does “Start Level” do as found in the SSA and LOG
instruments’ “Ln” settings menu?
Answer
The “Start Level” setting indicates where the histogram
table from which Ln data is calculated begins. The table
only has a range of 128 dB yet the 824 can measure over a
150 dB range when the Gain or Range settings are
considered. The default value for “Start Level” is 15 dB and
provides Ln data and SPL histograms from 15 dB up to
142.9 dB.
“Start Level” is also used with the main weighted Leq in the
Time History. Due to internal data encoding, the range is
limited to 127 dB and uses “Start Level” to determine the
desired measurement range. Since the time history is a data
logging function and the likelihood of changing the Gain or
Range setting is slim, this is sufficient range. The other
Residual RT-60
0.00
10
0.01
00
0.10
00
1.00
00
10 100 100
0
100
00
100
000
Hz
Seconds