A command to draw the selected Spectrogram object(s) into the Picture window in shades of grey.
Settings

From time (s)

To time (s)

the time domain along the x axis.

From frequency (Hz)

To frequency (Hz)

the frequency domain along the y axis.

Dynamic range (dB)

The global maximum of the spectrogram (after preemphasis) will always be drawn in black; all values that are more than Dynamic range dB below this maximum (after dynamic compression) will be drawn in white. Values inbetween have appropriate shades of grey.

Preemphasis (dB/octave)

determines the steepness of a highpass filter, i.e., how much the power of higher frequencies will be raised before drawing, as compared to lower frequencies. Since the spectral slope of human vowels is approximately 6 dB per octave, the standard value for this parameter is +6 dB per octave, so that the spectrum is flattened and the higher formants look as strong as the lower ones.

Dynamic compression

determines how much stronger weak time frames should be made before drawing. Normally, this parameter is between 0 and 1. If it is 0, there is no dynamic compression. If it is 1, all time frames (vertical bands) will be drawn equally strong, i.e., all of them will contain frequencies that are drawn in black. If this parameter is 0.4 and the global maximum is at 80 dB, then a frame with a maximum at 20 dB (which will normally be drawn all white if the dynamic range is 50 dB), will be raised by 0.4 * (80  20) = 24 dB, so that its maximum will be seen at 44 dB (thus making this frame visible).
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© ppgb, September 16, 2003