Wide Passband Design for Cosine-Modulated Filter Banks in Sinusoidal Speech Synthesis

A new filter design strategy to shorten the length of the filter is introduced for sinusoidal speech synthesis using cosine-modulated filter banks. Multiple sinusoidal waveforms for speech synthesis can be effectively synthesized by using pseudo-quadrature mirror filter (pseudo-QMF) banks, which are constructed by cosine modulation of the coefficients of a low-pass filter. This is because stable sinusoids are represented as sparse vectors on the subband domain of the pseudo-QMF banks and computation for the filter banks can be effectively performed with fast algorithms for discrete cosine transformation (DCT). However, the pseudo-QMF banks require relatively long filters to reduce noise caused by aliasing. In this study, a wider passband design with a perfect reconstruction (PR) QMF bank is introduced. The properties of experimentally designed filters indicated that the length of the filters can be reduced from 448 taps to 384 taps for 32-subband systems with less than -96dB errors where the computational cost for speech synthesis does not significantly increase.