Glottal flow: models and interaction

Abstract

The present article summarizes recent work at the Royal Institute of Technology in Stockholm on glottal flow models and source-filter interaction. A four-parameter model of the glottal flow derivative (Fant, Liljencrants & Lin, 1985) has been introduced. It incorporates a return phase after the instant of maximum closure discontinuity, the effective duration of which is inversely related to a spectrum fall-off parameter. The interaction of supraglottal pressure build-up and glottal flow profile accounts for a dependency of voice source characteristics on the vocal-tract filter function (Fant, Lin & Gobl, 1985). The F1 component of supraglottal pressure conditions a substantial part of the interaction. It is demonstrated that a phonation with F1 close to F0 minimizes air consumption, as suggested by Rothenberg (1985). This is also to a less degree found when F1 comes close to 2F0. Other interaction phenomena discussed are the occasional occurrence of a double peak in the glottal flow derivative and perturbations in the wave shape and amplitude of successive glottal flow pulses. At a high pitch, it is the supraglottal pressure build-up from previous periods that dominates the interaction. Glottal friction does not contribute much to the flow waveform and its excitational power.