A command available in the Spectrum menu if you select one or more Sound objects. It tries to compute an Ltas of the spectral envelope of the voiced parts, correcting away the influence of F0 in a way that does not sacrifice frequency selectivity. The resulting Ltas is meant to reflect only the resonances (formants) in the vocal tract and the envelope of the glottal source spectrum.
The analysis method is described in Boersma & Kovacic (2006).
© ppgb, December 3, 2006