Unconstrained Pitch Contour Modification Using Instants of Significant Excitation

This paper proposes a flexible method for pitch contour modification using the instants of significant excitation of the vocal tract system during the production of speech. The instants of significant excitation correspond to the instants of glottal closure (epochs) in the case of voiced speech, and to some random excitations like onset of burst in the case of nonvoiced speech. Instants of significant excitation are computed from the Linear Prediction (LP) residual of speech signals by using the property of average group-delay of minimum phase signals. The modification of pitch contour is achieved by manipulating the LP residual with the help of the knowledge of the instants of significant excitation. The modified residual is used to excite the time-varying filter, whose parameters are derived from the original speech signal. Perceptual quality of the synthesized speech is good, and is without any significant distortion. The proposed method is evaluated using waveforms, spectrograms and listening tests. Listening tests are performed on voice conversion application, where the source speaker’s pitch contour is modified by the proposed method according to the target speaker’s pitch contour. The performance of the proposed method is compared with Linear Prediction Pitch Synchronous Overlap and Add (LP-PSOLA) method using listening tests, for the voice conversion application.