Oba; Ln Percentiles - Larson Davis SoundAdvisor 831C Reference Manual

6.2.3 OBA

FIGURE 6-5 Setup Manager: OBA Settings
Normal (120 dB full
scale) and High (140 dB
full scale)
Select 1/1 Octave
bandwidth, 1/3 Octave
bandwidth, or both
simultaneously.
For measurement
TAKE NOTE
range specifications, see
Table A.5, "Octave Band
Analysis 1/1 Octave Linearity
Range," on page 9-A.

6.2.4 Ln Percentiles

SoundAdvisor Model 831C
The Maximum Specification has two options:
Bin Max
When set to Bin Max, it is the maximum value which occurred during
the entire measurement for that frequency band. Since individual
frequency bands may reach their maximum levels at different times,
this spectrum might be one which never occurred at any instant during
the measurement period.
At Lmax
When set to At L , it is the instantaneous spectrum at the moment
max
when the broadband maximum occurred (such as L
The Ln value is the sound level that has exceeded n% of the total
measurement time. For example, a value of n=90%, a displayed value
for L90 of 35dB means that for 90% of the measurement period the dB
level was at or above 35dB. These statistical values are commonly used
to describe the characteristics of non-steady sound such as
environmental noise.
In order to be able to calculate Ln values, the SoundAdvisor creates an
amplitude distribution table over the range 0 to 200 dB, in amplitude
increments of 0.1 dB. This data permits the calculation of Ln values for
any value of n in the range 00.01 to 99.99%.
Setup Manager
Choose the weighting for
the 1/1 Octave and/or 1/3
Octave bandwidth
frequency analysis: A, C, Z.
Spectral Ln values can be
measured using 1/1 or 1/
3 octave bandwidths. If
both 1/1 and 1/3 are
selected, Spectral Ln will
only measure for 1/3
bandwidth.
).
ASmax
6-5