In this contribution a novel method enabling high-quality speech modifications is presented; it is based on a harmonic + noise, (HNM), representation of the speech signal. The harmonic part is modelled by harmonically related sinewaves with slowly varying amplitudes, and frequencies. The noise part is modelled by an AR model and it is modulated by a time-domain amplitude envelope. Both the analysis and the synthesis are pitch-synchronous. Thanks to this twofold representation (Harmonic + Noise part), and to the pitch-synchronous scheme, a flexible technique for time-scale and pitch-scale modifications, inspired by PSOLA methods, can be applied, yielding high-quality modification.
Bibliographic reference. Stylianou, Yannis / Laroche, Jean / Moulines, Eric (1995): "High-quality speech modification based on a harmonic + noise model", In EUROSPEECH-1995, 451-454.