Frequency-warping in speech

We present results that indicate that the formant frequencies between different speakers scale differently at different frequencies. Based on our experiments on speech data, we then numerically compute a universal frequency-warping function, to make the scale-factor independent of frequency in the warped domain. The proposed warping function is found to be similar to the mel-scale, which has previously been derived from purely psycho-acoustic experiments. The motivation for the present experiments stems from our proposed use of scale-transform based cepstral coefficients (Umesh et al., 1996) as acoustic features, since they provide superior separability of vowels than mel-cepstral coefficients