The spectrogram menu

The menu allows the calculation and the display of spectrograms of different types.

The menu commands

Wide band: See just below

Narrow band: Wide and narrow band spectrograms are two FFT spectrograms distinguished by their signal and FFT windows.

LPC: Spectrogram calculated after an operation of linear prediction by auto-correlation.

Cepstral smoothing: Spectrogram calculated by cepstral smoothing.

Critical bands: Spectrogram filtered by critical bands (Bark or Mel) and displayed on either a linear or perceptive scale.

Reassigned: The energy of spectrogram is reassigned to remove the influence of the temporal and frequency window. See the paper of  Plante et al. for further details (F. Plante and G. Meyer and W.A. Ainsworth", "Improvement of speech spectrogram accuracy by the method of reassignment", "IEEE Transactions on Speech and Audio Processing", 6(3), pp 282-287, 1998). To obtain best results set the “Upper disp. Frequency” (see below) to 2000 Hz approximately, set the FFT order to 4096 (in the “Option” submenu). If the window is small (4ms) the time resolution is increased and enables the detection of glottal closure instants. If the window is longer (32 ms for instance) very fine harmonics are obtained.

Copy to clipboard: copy the bitmap of the current spectrogram into the clipboard.

Save spectrogram (pgm file): save the spectrogram into a pgm file (the spectrogram is rotated 90 degrees).

Clear: Erase the spectrogram.

Keep decoration: Bind the “decoration” to the spectrogram (See command below).

Clear decorations: Remove the elements of decoration (formants, cepstral peaks, LPC roots) from the spectrogram with the exception of those which were present during the last execution of “Keep decoration”.

Options: Permits the modification of the spectral parameters used in calculating the spectrogram.

Upper disp. Frequency: Allows the upper frequency of the spectrogram to be modified. This frequency is used for all the spectral display commands including those of the spectral slice. User has to pay attention to set calculation parameters of spectra according to this frequency to get a nice spectral display.

Wide Band, Narrow Band, LPC, Cepstral Smoothing, Draft, Reassigned, Critical bands: set the options for the calculation of the corresponding spectrograms.

Defaults: