NTi Audio XL2 Sound Level Meter - Manual (Page 80)

80
Reverberation Time RT60
18 Correlation Factor in %
The correlation factor is 100% for perfectly linear sound
pressure level decay after the sound source has ceased.
The natural deviation from this linearity results in lower
correlation values. The correlation factor is typically 80 -
100%.
19 Cycle Reverberation Time Test Result
Readout of cycle reverberation time and correlation factor
18 when selection 17 is CYC xx or Last.
Correlation Factor. Scale is on the right Y-axis. For
more details see
18 .
Reverberation time measurement result of individ-
ual displayed cycle. Scale is on the left Y-axis.
20 Y-Axis Correlation Factor
The right Y-axis shows the correlation factor in %. The cor-
relation factor Y-axis is displayed when test result selection
17 is CYC xx or Last.
21 Delete Cycle Results
Individual cycle results may be deleted, thereby excluding
them from the calculation of the AVRG result.
Test Signals
The sound source shall be as omnidirectional as
possible. Use either a gated pink noise or an
impulse source as the test signal.
Gated pink noise •
Various gated pink noise test signals with
different on/off times are offered by the NTi
Audio Test CD included with the XL2 or the
Minirator signal generator.
Impulse •
The trigger signal is a generated impulse
source, such as a starter pistol. Individual
measurements, or test sequences with re-
peated trigger signals, can be carried out.
Ideally the XL2 should measure the reverbera-
tion time of several on/off cycles and automati-
cally average the reverberation time results. The
uncertainty factor is calculated after a minimum
of three measurement cycles.