A Control of Fundamental Frequency Contour for Hidden Markov Model-Based Thai Speech Synthesis

Problem statement: In the conventional HMM-based speech synthesis system for Thai, there is no control of fundamental frequency control in the synthesis stage. The tone correctness of the synthesized speech is unacceptable due to the imbalance of training data of all tones. Approach: This study proposes a mathematical model to control the F₀ contour of the synthesized speech. This control is proposed to correct only some distorted segments of the F₀ contour which occur within some syllables due to lacking of training data for some tones. Results: An experimental result compares F₀ contours between those of synthesized speech with and without tone-type questions; furthermore the size of Thai speech corpus is varied to investigate the synthesized speech quality. A mathematical model is applied to control the F₀ contour. By using the proposed control, the correction of the F₀ contour is obviously shown in the experimental results. Conclusion: The control of F₀ contour has been proposed. It can noticeably improve the tone correctness of the synthesized speech.