A Technique for Analysing Voice Quality in Pathological and Normal Speech

A technique for voice source analysis is described which is currently being used to study voice quality variation, in dysphonic and normal speakers. The analysis technique involves a two-step procedure. The first, inverse filtering of the speech pressure waveform, yields the differential glottal flow. The settings for the inverse filter are initially estimated using a pitch-synchronous semi-automatic procedure based on the covariance method of LPC. The filter is then interactively edited on a pulse-by-pulse basis to correct for errors to which current automatic procedures are prone. The second step in the analysis involves matching a voice source model (the Liljencrants-Fant model) to the output of the inverse filter, again on a pulse-by-pulse basis. This allows quantification and comparison of the salient voice source characteristics. An illustration of some voice quality variation in normal and dysphonic speech is presented.