The ineffectiveness of larynx movement

Abstract

Vertical movement of the larynx has been held responsible for two effects in speech production: a noticeable change in intraoral air pressure (P0) as a result of contraction or expansion of the oral cavity and perturbation of the fundamental frequency (F0) of neighboring vowels as a result of changes in the vertical tension of the vocal folds. Raising the larynx is supposed to elevate both P0 and F0, while lowering the larynx is supposed to reduce both parameters. Simultaneous measurements of larynx movement and P0 during the production of voiced and voiceless stops and ejectives by three speakers of Tigrinya showed that the larynx moves much too slowly to have any significant effect on P0. Computer simulation of the stops of this language confirmed this result. Larynx movement also could not be responsible for the perturbation of F0 in vowels following stops in Tigrinya since F0 was either not elevated or even depressed after stops which are produced with larynx raising, the voiceless stops, and ejectives. F0 was only weakly positively correlated with larynx height after voiced stops—both low, uncorrelated after voiceless ones, and negatively correlated after ejectives—F0 low and the larynx high. These results Suggest that movement of the larynx during a stop is at best a passive response to other, probably oral, articulations and that the tension of the vocal folds is not directly perturbed by changes in larynx height either.