A study of two-formant models for vowel identification

Abstract

An experiment has been performed where various two-formant models reported in the literature were assessed as to their ability to predict the formant frequencies obtained in a vowel identification task. An alternative model is proposed in which the auditory processing of vowel sounds is assumed to take place in two stages: a peripheral processing stage and a central processing stage. In the peripheral stage the speech spectrum is transformed to its auditory equivalent and the formant frequencies are extracted from this spectrum using a peak-picking mechanism. The central stage performs a two-formant approximation on the results of the first stage operation, and it is this formant pair that vowel identification is taken to operate on during vowel perception. The first and second formant frequencies of this two-formant model are taken to be equal to the first and second formant frequencies extracted at the first stage plus a perturbation term which accounts for the interaction effects of the neighbouring formants. The perturbation caused by each of these neighbouring formants is inversely proportional to its separation from the main formants. This model compares favourably with previous models in its prediction of the formant frequencies obtained from the vowel identification task.