This paper introduces a novel method to improve the U/V decision method in HMM-based speech synthesis. In the conventional method, the U/V decision of each state is independently made, and a state in the middle of a vowel may be decided as unvoiced. In this paper, we propose to utilize the constraints of natural speech to improve the U/V decision inside a unit, such as syllable or phone. We use a GMM-based U/V change time model to select the best U/V change time in one unit, and refine the U/V decision of all states in that unit based on the selected change time. The result of a perceptual evaluation demonstrates that the proposed method can significantly improve the naturalness of the synthetic speech.
Bibliographic reference. Kang, Shiyin / Shuang, Zhiwei / Duan, Quansheng / Qin, Yong / Cai, Lianhong (2009): "Voiced/unvoiced decision algorithm for HMM-based speech synthesis", In INTERSPEECH-2009, 412-415.