Patent ID: 6029128
Filing Date: 2000-02-22
Classification: G10L

Abstract:
A synthesiser for speech synthesis, comprising:an excitation source; anda post-processing means coupled to said excitation source for operating on a first signal including speech periodicity information derived from said excitation source, wherein the post-processing means modifies the speech periodicity information content of the first signal in accordance with a second signal derivable from said excitation source in order to produce an enhanced synthesised speech signal;wherein the post-processing means comprises gain control means for scaling the second signal in accordance with a first scaling factor (p) derivable from pitch information associated with the first signal;wherein the excitation source comprises a fixed code book and an adaptive code book, the first signal comprising a combination of first and second partial excitation signals respectively originating from the fixed and adaptive code books, the second signal being substantially the same as the second partial excitation signal and originating from the adaptive code book, the first signal being modified by combining the second signal with the first signal, and the first scaling factor (p) being derivable from an adaptive code book gain factor (b) in accordance with the following relationship, ##EQU13## where TH represents threshold values, b is the adaptive code book gain factor, p is the first post-processing means scale factor, a.sub.enh is a linear scaler and f(b) is a function of the adaptive code book gain factor b, andwherein the post-processing means further comprises an adaptive energy control means adapted to scale a modified first signal in accordance with the following relationship, ##EQU14## where N is a suitably chosen adaption period, ex(n) is the first signal, ew' (n) is a modified first signal and k is an energy scale factor.