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Once the measurement is completed, the energy decay curves are plotted. Use the arrows
to cycle through the frequency bands (note that you can choose whether to measure in 1/1
or 1/3 octave bands through the "settings" screen).
RT60 decay curves plotted once the measurement is completed
Inspect the decay curves to visually verify that the measurement is correct. An incorrect
measurement (which should be rejected) may become apparent in any of the following
ways:
•
The plotted data points do not reflect the expected linear decay of energy:
the level does not decrease linearly over time. If this happens, the triggering
process may have been disrupted.
•
The linear decay curve that is fitted (drawn line) does not match the
displayed data points. E.g., the starting point of the decay curve may be off.
•
The signal-to-noise ratio (difference between the steady-state noise signal
and the system noise floor) is insufficient.
From the decay curves, three different reverberation time metrics are calculated:
•
The EDT (Early Decay Time), based on the first 10 dB of decay
•
The T20, based on the section of the decay curve between -5 dB and -25 dB
•
The T30, based on the section of the decay curve between -5 dB and -35 dB
Each of these three metrics has its own linear decay curve fit through the data points. The
values of the EDT, T20 and T30 can be seen on the second screen of the RT60 module.
Note that the reverberation time usually differs significantly between different frequency
bands. Also note that (although respectively measured over 10, 20 and 30 dB of decay) the
values of EDT, T20 and T30 are always extrapolated to 60 dB of decay; hence the name
T60: the time it takes for the energy to decay to a level 60 dB below the starting level.
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VOX -01 Operating Manual
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