RESEARCH ON THE DEVELOPMENT OF SPEECH QUALITY EVALUATION SYSTEM FOR THE PURPOSE OF EDUCATION AND TRAIN

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The final target of this research is to develop an objective speech quality evaluation system based on the acoustic analysis of speech. It is planed that the evaluation does not depend on the subjective method and the system can by used for the education of language and train of utterance. But this project is limited to evaluate speech uttered by patients of orthodontic treatment, because there are too many factors relate to the general speech.By such the limitation, the speech quality varies only by the following three changes, the first one is the change in the vocal tract length, the second one is the change in the tong movement and the third one is the limitation of tong movement by the tong side appratus for the cure. Those changes are considered to affect mainly on the first and the second formant frequencies. The results of the subjective evaluation of speech uttered before and after the surgical operation are compared to the changes in the formant locus. And comparatively high … More correlation was observed between the result of subjective evaluation and the changes in the formant locus expressed by numerical values with dynamic programming method. The same method was applied to the speech of patients with the tong side curing apparatus. Good correlation was observed with some patients. But the number of samples is too little to assert the effectiveness of the method. Further researches using more speech samples are necessary.On the other hand, the change in the high frequency spectral components is investigated according to the previous report in which the power of high frequency region increases by shorting the jaw. But we could not find so much change usable for the objective evaluation.Acording to the results of those investigation, an evaluation system is composed. The system display the loci of the lowest two local spectral peaks in the spectrum analyzed by LPC method and the correlation between the old utterance and the patients new utterance. But, there remain many problems to be investigated using more subjects. Less