A Two-Level Drive - Response Model of Non-stationary Speech Signals.

The transmission protocol of voiced speech is hypothesized to be based on a funda mental drive process, which synchronizes the vocal tract excitation on the trans mitter side and evokes the pitch perception on the receiver side. A band limited fundamental drive is extrac ted from a voice specific subband decom position of the speech signal. When the near periodic drive is used as fun damental drive of a two-level drive-response model, a more or less aperiodic voiced excitation can be recon struc ted as a more or less aperiodic trajectory on a low dimensional continuous syn chro nization manifold (surface) described by speaker and phoneme specific coupling functions. In the case of vowels and nasals the excitation can be described by a univariate coupling function, which depends on the momentary phase of the funda mental drive. In the case of other voiced consonants the coupling function may as well depend on a delayed funda mental phase with a phoneme speci fic time delay. The delay may exceed the length of the analysis window. The resulting long range correlation cannot be analysed or synthesized by models assuming stationary excitation. [ABSTRACT FROM AUTHOR]