Modeling of variations in cepstral coefficients caused by F0 changes and its application to speech processing
Nobuaki Minematsu, Seiichi Nakagawa · 1998
In this paper, the correlation between spectral variations and F0 changes in a vowel sound is rstly analyzed, where the variations are also compared to VQ distortions calculated in a ve-vowel space. It is shown that the F0 change approximately by a half octave produces the spectral variation comparable to the averaged VQ distortion when the codebook size is the number of the vowels. Next, a model to predict the cepstral coe cients' variations caused by the F0 changes is built based on the multivariate regression analysis. Experiments show that the generated frame by the model has a remarkably small distance to the target frame and that the distance is almost the same as the VQ distortion with the codebook size being 10 to 20. Furthermore, the model is evaluated separately in terms of a spectral envelope predictor with a given F0 and a mapping function of feature sub-spaces. It is indicated that, while the models should be built dependently on phonemes and speakers as a spectrum predictor, adequate selection of parameters can enable the speaker/phoneme-independent models to work e ectively as a mapping function.