HD2010UC
- 19 -
V4.2
S
TATISTICAL
G
RAPHS
The functioning mode with
advanced statistical analyser,
available with “Advanced Data
logger” installed, allows analyses on the sound pressure level with FAST time constant (sampled 8
times per second) or short equivalent level (integrated every 0.125s) or peak level (calculated twice
per second) with any frequency weighting (only C or Z for peak level).
The statistical analysis is done with 0.5dB classes for sound levels from 21dB to 140dB and
provides graphic display of the sound level distribution of probabilities and percentile levels. The
graphs can be enabled in Menu >> Statistical Analyzer >> Display Statistics. Disabling the displays
does not influence the programmable L1–L4 percentile level calculation.
The following figure shows the level
distribution of probabilities
on the 6-minute measure-
ment of the noise issued by a climatic room. During measurement an acoustic calibrator was
switched on for about 2 minutes near the microphone.
The distribution of probabilities shows the different “population” of the examined noise clear-
ly. From lower levels, the first peak (about 63dBA) reflects the room background noise caused by
the ventilation system. The second peak (about 65dB) concerns the cooling compressor activation.
The third peak (about 69dB) is the tone issued by the calibrator.
In the following figure the
cumulative distribution
for the same sample above can be seen.
The cumulative distribution is built from the 100% of the levels under the measured minimum, and
subtracting the probability of each you get 0 for the levels over the measured maximum.
The
percentile levels
are calculated interpolating the cumulative distribution.
The statistical analyzer resets the classes at the beginning of measurement and, if no report time has
been selected, it will continue accumulating the statistic until the end of the measurement. If a re-
port time is selected (menu Main >> Measurement >> Report time) or the “multi” mode is activat-
ed, the statistic is automatically reset at the beginning of each interval.
Summary of Contents for DeltaOHM HD2010UC
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