Norsonic nor118, Instruction Manual

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56 Chapter 10
Reverberation time measurements
57 Norsonic Nor118
User Guide
You will note a horizontal line located 30 dB below the
displayed top scale. Remember that the displayed top scale
is purely a display feature and not related to the measure-
ment range setting.
is line represents the trigger level threshold for the
impulse decay capture.
4
Use the + and – keys (the  and  keys) to change
the trigger level threshold in 10 dB steps, if applica-
ble.
Reverberation time setups cannot be stored and there
should be no need to either, since the only things to set
up are the trigger frequency band and the trigger level
threshold.
To make a reverberation time measurement:
• Press the  key and generate the impulse. While
the instrument waits for the trigger condition to
be fulfilled, a
W
() is displayed. Once the
instrument detects a level above the threshold in the
frequency band you have specified, the capture of the
impulse and its decay will begin. An
R
will appear in
the display when the measurement is running.
Once you have pressed the  key the trigger setting
cannot be changed, even if the measurement is not yet
running. To be able to change these settings you must
terminate the ongoing measurement.
To terminate an ongoing measurement:
• Press  or /. In both cases the instrument
will return to  mode.
e instrument will measure for 10 seconds and count
down to 0 to indicate how much is left of the measurement.
e acquired results are then presented as a table.
e table shows the calculated reverberation time
for each frequency band and for the spectral weighting
networks (- and - or -weighting). If the reverberation
time measured is too short compared to the minimum
Frequency bands above 10 kHz are
not measured!
Although the instru-
ment has filters covering the frequency range up to
20kHz (expressed as filter band centre frequency),
reverberation time calculations are made up to
10 kHz only. ose above are shown in the table as
well, but no values are presented.
The reverberation times measured are presented tabulated
and are all in seconds, as shown here.
Values missing are shown
like this. Frequency bands
not measured will look like
this. The same applies to
frequency bands where no
value was obtainable.
If the background noise level
is too high, or the calculated
reverberation time is shorter
than the limit (see side bar
Minimum reverberation times
for more on this) a question
mark appears next to the
dubious value(s).
Navigate in the table by
using the
keys
to see values of other
frequency bands.