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: