Investigations of independence of distortion scales in objective evaluation of synthesized speech quality
Haruaki Yabuoka, Takeshi Nakayama, Yukio Kitabayashi, Yoshiaki Asakawa · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 2000
Using factor analysis, we have investigated the independence of five distortion scales, namely, differential spectrum distortion, phase distortion, waveform distortion, cepstrum distance, and amplitude distortion, that are widely used in the objective evaluation of synthesized speech quality. We have found that the above distortion scales can be constructed from two factors. The first factor is constructed from cepstrum distance, amplitude distortion, and waveform distortion, and the second factor is constructed from phase distortion and differential spectrum distortion. When a multiple linear regression model is used as a prediction model of MOS, the prediction accuracy is the highest when the cepstrum distance is used as the distortion scale for the first factor and the differential spectrum distortion for the second factor. Investigating the correspondence of psychological quality factors with the physical distortion factors, it was found that the first physical factor is related to “clarity” and second factor is related to “sensation.” Moreover, the importance of differential spectrum distortion in the future quality prediction of low-bit-rate synthesized speech is demonstrated. © 2000 Scripta Technica, Electron Comm Jpn Pt 3, 83(5): 14–22, 2000