The Neuromuscular Phonatory Control System and Vocal Function

Abstract

This paper reports on recent studies supposed to answer the question, whether there exists a relationship between the ability of kinesthetic voice control, i.e. the operational efficiency of the neuromuscular phonatory control system, and the quality of vocal function. In three subject groups with differing qualities of vocal function (24 singers, 33 vocally untrained persons and 30 patients with hyperfunctional dysphonia) pitch and intensity changes of the speaking and singing voice were studied during interruption of auditory feedback by increasing binaural masking (white noise of 60, 80, 100 and 110 dB SPL) by means of our recently developed fundamental frequency analyser. The following results were obtained: the increase in speech intensity level was similar in all groups, but the elevation of mean speaking fundamental frequency differed significantly: the dysphonic group reacted to binaural masking with the greatest pitch increments and the vocally trained group (singers) with the smallest ones. Additionally, dysphonic patients showed a significant reduction in pitch variations (speech melody). Voice accuracy, i.e. the ability to reproduce a given reference tone under masking conditions, was found to be much better in singers than in the normal and the dysphonic group. Irrespective of the masking situation, dysphonic patients showed a distinctly poorer stability of the singing voice than vocally untrained subjects and the highest incidence of an incorrect pitch regulation (“initial overswing”) during sudden upward shifts of fundamental frequency. From these observations and on the basis of physiological data about pitch and intensity control, the following conclusions are drawn: the neuromuscular phonatory control system works more efficiently in vocally trained persons than in vocally untrained ones or, especially, in dysphonic patients, thus revealing that kinesthetic control ability is closely related to the quality of vocal function. As this ability can be measured by observing pitch changes under masking conditions, an objective evaluation of the individual vocal function by means of fundamental frequency analysis seems feasible.