Apparatus for synthesizing speech by varying pitch

Abstract From the Canadian patent

The pitch of synthesised speech signals is varied by separating the speech signals into a spectral component and an excitation component. The latter is multiplied by a series of overlapping window functions synchronous in the case of voiced speech, with pitch timing mark information corresponding at least approximately to instants of vocal excitation to separate it into windowed speech segments which are added together again after the application of a controllable time-shift. The spectral and excitation components are then recombined. The multiplication employs at least two windows per pitch period each having a duration of less than one pitch period. Alternatively each window has a …