High quality voice manipulation method based on the vocal tract area function obtained from sub-band LSP of straight spectrum

This paper describes a high-quality manipulation method of voice quality base on the vocal tract area function (VTAF) obtained from sub-band LSP of STRAIGHT spectrum. Our research group had developed the manipulation technique of voice quality based on VTAF that can generate natural formant transition. However, it is observed that the generated sound sometimes results in degradation when the input signal has a high sampling frequency. Therefore, we develop a new method that extracts VTAF properly from such input signal. This method firstly divides the input spectral envelope represented by STRAIGHT spectrum into lower and higher frequency bands, secondly extracts the Line spectrum pair (LSP) in each frequency band after spectral flattening that is appropriate for the frequency band, thirdly concatenates a pair of the sub-band LSP, and finally obtains VTAF from PARCOR coefficients converted from the concatenated LSP. A subjective experiment proved that the proposed method is high quality enough.