cepstrum
cepstra

    (Coined in a 1963 paper by Bogert, Healey, and
   Tukey) The Fourier transform of the log-magnitude spectrum:

   	fFt(ln( | fFt(window . signal) | ))

   This function is used in speech recognition and possibly
   elsewhere.  Note that the outer transform is NOT an inverse
   Fourier transform (as reported in many respectable DSP texts).

   [What's it for?]

   (1997-01-07)