The RT60 Reverberation Time curves at each octave or one-third octave filter centre frequency are displayed on this graph, with separate traces for the Early Decay time (EDT) and the 60dB decay times T20, T30 and REW's Topt. See below for descriptions of each of these parameters.

The control panel for the RT60 graph has these controls:

The *Time reversed filtering* control applies the octave band filters
backwards in time, this reduces the filter's own contribution to the measured
decay. When using 1/3 octave filters at low frequencies the filter decay time
can be significant, over 200 ms for a 100Hz 1/3 filter, for example. Applying
the filter in reverse reduces this decay to less than 50 ms, but it does affect
the response somewhat, such that Early Decay Time (EDT) figures using Time-Reversed
filters may not be valid.

*Zero phase filtering* applies 4th order bandpass filters in two passes
through the data, one forwards and one reversed, to give a response with overall zero
phase shift. This reduces the contribution of the filter's decay time similar to
time revered filtering but without significantly affecting early decay time.

If the *Show correlation factor* box is checked the graph legend names
shows the quality of the line fit for the various decay measures. The "r" value shown
after each decay measure is the regression coefficient, which measures how well the data
corresponds to a straight line. A value of -1 would indicate a perfect fit, values lower in
magnitude than -0.98 indicate the corresponding decay figure may not be reliable. Unreliable
values are italicised.
The decay measures available are:

- EDT
- Early Decay Time, based on the slope of the Schroeder curve between 0dB and -10dB.
- T20
- Decay time based on the slope of the Schroeder curve between -5dB and -25dB.
- T30
- Decay time based on the slope of the Schroeder curve between -5dB and -35dB.
- Topt
- An "optimal" decay time based on the slope of the Schroeder curve over a variable range chosen to yield the best linear fit. If the early decay time is much shorter than T30 the Topt measure uses a start point based on the intersection of the EDT and T30 lines, otherwise it uses -5dB. REW tests every end point in 1dB steps to the end of the Schroeder curve and chooses the one which gives the best linear fit. The range over which the value has been calculated is shown in the trace legend.

The RT60 plot can show horizontal bars centred on each filter frequency and
spanning the filter's bandwidth, or lines joining the filter centre frequencies,
according to the *Use bars on RT60 plot* control setting.

The reverberation times for the current measurement can be written to a text
file using the File -> Export -> *RT60 data as text* menu entry.