Articulatory Speech Synthesizer

ARTICULATORY SPEECH SYNTHESIZER Chang-Shiann Wu Department of Information Management Shih Chien University Kaohsiung, 845 Taiwan chwu4142@ms5.hinet.net Y u-Fu Hsieh HarveTech DSP Corporation LungTan TaoYuan, 325 Taiwan aliceufo@msl.hinet.net ABSTRACT The aim of this research was to develop a flexible, high quality articulatory speech synthesis tool. One feature of this research tool is the simulated annealing optimization procedure that is used to optimize the vocal tract parameters to match a specified set of formant characteristics. Another aspect of this study is the derivation of a new form of the acoustic equations. A transmission-line circuit model of the vocal system, which includes the vocal tract, the nasal tract with sinus cavities, the glottal impedance, the subglottal tract, the excitation source, and the turbulence noise source, was constructed. The acoustic equations of the vocal system were rederived for the proposed articulatory synthesizer. A digital time-domain approach was used to simulate the dynamic properties of the vocal system as well as to improve the quality of the synthesized speech. 1. INTRODUCTION Articulatory synthesis is the production of speech sounds using a model of the vocal tract, which directly or indirectly simulates the movements of the speech articulators. It provides a means for gaining an understanding of speech production and for studying phonetics. In such a model coarticulation effects arise naturally, and in principle it should be possible to deal correctly with glottal source properties, interaction between the vocal tract and the vocal folds, the contribution of the subglottal system, and the effects of the nasal tract and sinus cavities. Articulatory synthesis usually consists of two separate components. In the articulatory model, the vocal tract is divided into many small sections and the corresponding cross-sectional areas are used as parameters to represent the vocal tract characteristics. In the acoustic model, each cross-sectional area is approximated by an electrical analog transmission line. To simulate the movement of the vocal tract, the area functions must change with time. Each sound is designated in terms of a target configuration and the movement of the vocal tract is specified by a separate fast or slow motion of the articulators. A properly constructed articulatory synthesizer is capable of reproducing all the naturally relevant effects for the generation of fricatives and plosives, modeling coarticulation transitions as well as source-tract interaction in a manner that resembles the physical process that occurs in real speech production. Articulatory synthesizers will continue to be of great importance for research purposes, and to provide insights into various acoustic features of human speech. 2. REALIZATION OF THE ARTICULATORY MODEL Geometric data concerning the vocal tract is essential to our understanding of articulation, and is a key factor in speech production. According to the acoustic theory of speech production, the human vocal tract can be modeled as an acoustic tube with nonuniform and time-varying cross-sections. It modulates the excitation source to produce various linguistic sounds. The success of articulatory modeling depends to a Figure 1:� Articulatory model's parameters and midsagittal grids. large extent on the accuracy with which the …

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