Spectral Decay Graph

This graph shows spectral decay traces over the region from 10Hz to the end of the measurement sweep. The plot used logarithmically spaced data at 96 points per octave with 1/48th octave smoothing applied. The Spectral Decay plots are generated by shifting the impulse response window to the right by the slice interval to generate each succeeding slice. Two windows are used, a left side window to taper the data prior to the start of the region being analysed and a right side window that spans the selected window width. The default window type for the left side is Hann, for the right side it is Tukey 0.25, other types may be selected via the Spectral Decay entries in the Analysis Preferences. The initial reference point for the windows (end of left window/start of right window) is the peak of the impulse response.

To produce the Decay plot click the Generate button in the bottom left corner of the graph area.

Decay Controls

Decay Controls

The traces for each slice can be drawn as conventional lines or as filled areas, selected by the Fill slices check box. The alternative views are shown below.
Spectral Decay, normal traces
Spectral Decay, filled traces

The time separation of the slices is controlled by the Slice Interval setting, the width of the impulse response section that is used to generate the slice is set by the Window control. The corresponding frequency resolution is shown at the bottom of the controls panel.

The control settings are remembered for the next time REW runs. The Apply Default Settings button restores the controls to their default values.

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