Frequency-warping in speech

In this paper we present results that indicate that the formant frequencies between di erent speakers scale di erently at di erent frequencies. Based on our experiments on speech data, we then numerically compute a universal frequencywarping 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 recently proposed use of scale-transform based cepstral coe cients [6] as acoustic features, since they provide superior separability of vowels than mel-cepstral coe cients.