Effect of voice quality on frequency-warped modeling of vowel spectra

The perceptual accuracy of an all-pole representation of the spectral envelope of voiced sounds may be enhanced by the use of frequency-scale warping prior to LP modeling. For the representation of harmonic amplitudes in the sinusoidal coding of voiced sounds, the effectiveness of frequency warping was shown to depend on the underlying signal spectral shape as determined by phoneme quality. In this paper, the previous work is extended to the other important dimension of spectral shape variation, namely voice quality. The influence of voice quality attributes on the perceived modeling error in frequency-warped LP modeling of the spectral envelope is investigated through subjective and objective measures applied to synthetic and natural steady sounds. Experimental results are presented that demonstrate the feasibility and advantage of adapting the warping function to the signal spectral envelope in the context of a sinusoidal speech coding scheme.