Norsonic nor118, Instruction Manual

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18 Chapter 4
Simple sound measurements
19 Norsonic Nor118
User Guide
To produce the measurement duration setup menu:
• Press  > 2. To leave the menu press the 
key.
Statistics
Even if your instrument is equipped with the optional
extension 4 – statistics, the percentiles table will fail to
produce values for all percentile settings unless the meas-
urement duration is sufficiently long – see the Missing
percentiles side bar below left for more on this.
The sound level meter display
Elapsed
duration
Time constant
and function
displayed
Spectral
weighting
networks
applied
Measured
values
Display top
scale
Preset duration
Measurement
running
Datum (lower
end of bar
graph
Measurement duration setup menu
Measurement duration setup menu when time profile
option is installed (left), and when it’s not (right).
Missing percentiles?
ere may be
percentiles that fail to produce values in
the table. is is because you have not measured for
a time long enough to provide the necessary number
of samples.
Statistical sampling – which should not be con-
fused with the sampling of the analogue-to-digital
conversion – takes place 10 times a second. For
comparison, the sampling of the analogue-to-dig-
ital conversion runs at 48 kHz!
Since the statistical sampling takes place 10
times a second, it will take 10 seconds to produce
100 samples. You will need at least 100 samples to
be able to calculate the 1% percentile.
Likewise, for the 0.1% percentile the minimum
time required will be 100 seconds. Measurements
whose duration are shorter than these minimum
limits will not produce percentile values for all pos-
sible settings of the percentiles.
Going to measure very high levels?
As an optional extension the Nor118 is
able to measure very high sound pressure levels
without changing the microphone cartridge – see
High levels in the Technical specifications for details.