Study on Natural Voice Synthesis based on Analysis of the Articulation Organ.

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Natural voice synthesis is an important project for developing the voice processing system and the articulation prosthesis system. The vocal cords and the vocal tract are two elementary organ in the voice articulation system. Naturality of language such as accent and intonation depend on the pitch control in the vocal cords. Significance of the vocal tract control in articulation is self-evident. We have analyzed articulation system by several methods such as measurement of articulation movement. PARCOR analysis, measurement of throat impedance and vocal tract imaging using magnetic resonance(MRI). In this project, later two methods are discussed.(1)A throat impedance-meter was developed for measuring resistance and capacitance components separately. Stational characteristics between vocal pitch and impedance could be approximated by a third order polynomial function. Dynamic characteristics between vocal pitch and impedance was analyzedby FFT to estimate pitch from impedance change. S … More ynthesized vowels using estimated pitch accorded with original vowels in hearing test. In the case of sequential vowels, vocal pitch could be estimated by compensating impedance component arising from change of the vocal sound. For most part of the subjects whose resistance change did not accompanied with vocal pitch, capacity change was effective for pitch estimation. It was supposed that this variance should depend on parsonality in the articulation.(2)Three dimensional shapes of vocal tract and nasal cavity were measured using MRI.Especially, image of dental crowns containing low hydrate content was obtained by covering them with thin dental crown plate. Using this method, distance between molars could be measured in accuracy below 0.4 mm. Arbitrary sections of the vocal tract and nasal cavity could be extracted by applying cubic convolution method to 3D images during articulating Japanese vowels and fricatives(/s/, /sh/, /shu/). It was revealed that there existed parsonal differences in the situation of the dental crowns and volume of the paranasal cavities during articulation. Less