Prediction of perceived phonetic distance from critical-band spectra: A first step

Judgements of phonetic distance between pairs of static synthetic vowels and fricatives have been collected in which the stimulus ensemble included formant frequency changes and a number of acoustic changes that turn out to have little phonetic relevance (e.g. spectral tilt, relative formant amplitudes, high-pass, low-pass, and notch filtering). These data can be used to evaluate a spectral distance metric. For example, distance calculations based on the sum-of-squares of differences in critical-band filter bank outputs and those based on the linear-prediction residual correlate poorly with the vowel distance-judgement data. On the other hand, a metric based on spectral slope differences near the peaks in the critical-band spectra to be compared can be made to correlate very well (0.93) with the perceptual data.