Impulse train equivalent excitation signals for high‐quality speech synthesis

Abstract

AbstractIn the speech synthesis using filters, other than the impulse train, some special pulse trains such as an excitation signal are used, especially the pulse train by Barker sequence and the pulse train obtained by averaging in time the energy of the signal. However, they do not produce a high‐quality synthesized speech. By contrast, the possibility exists that a high‐quality speech synthesis can be achieved by utilizing the residual speech as the excitation signal. In this case, a certain data compression must be applied to the residual signal. Several useful methods are known for coding the residual speech, such as base‐band signal coding and multipulse coding. For efficient speech data compression or realization of high‐quality speech synthesis by a rule‐based speech synthesis, the lack of rules or formulation for the excitation source is a serious problem. To realize a high‐quality speech synthesis by a rule‐based excitation, a high‐quality impulse train equivalent excitation signal is needed to replace the usual impulse train. From such a viewpoint, this paper first performed the very‐short‐term analysis of the residual speech, confirming that the spectral envelope of the voiced sound interval varies with time in quite a characteristic way. A method of generating the impulse train equivalent signal (FTSITES) with the spectral envelope and fine‐time structure is proposed according to the result of analysis. It is shown that a high‐quality speech synthesis is achieved by utilizing FTSITES as the excitation signal.