Frequency warped modeling of vowel spectra: Dependence on vowel quality
The compact representation of harmonic amplitudes in the sinusoidal coding of speech is an important problem in low bit rate speech compression. A widely used method to achieve this is by the all-pole modeling of the spectral envelope. Often a perceptually warped frequency scale is applied in the all-pole modeling to improve perceived accuracy at low model orders. In this work, an attempt is made to obtain a suitable frequency scale warping function by an experimental study on synthetic and natural steady vowels. Subjective listening experiments indicate that the change in perceived quality brought about by frequency warping depends on the underlying signal spectrum or vowel quality. Objective distortion measures are computed to obtain insights into the subjective results. It is observed that an auditory distance measure based on partial loudness shows high correlation with the subjective test scores indicating that frequency masking plays an important role in spectrum envelope modeling. (c) 2005 Elsevier B.V.. All rights reserved.
frequency warping all-pole modeling partial loudness spectral envelope modeling