Methods for nonlinear spectral distortion of speech signals

The spectral distortion of speech signals, without affecting the pitch or the speed of the signal, has met with some difficulty due to the need for pitch extraction. This paper presents a general analysis-synthesis scheme for the arbitrary spectral distortion of speech signals without the need for pitch extraction. Linear predictive warping, cepstral warping, and autocorrelation warping, are given as examples of the general scheme. Applications include the unscrambling of helium speech, spectral compression for the hard of hearing, bit rate reduction in speech compression systems, and efficiency of spectral representation for speech recognition systems.