An Analog Study of Cleft Palate Speech

Abstract

The production of plosive and fricative sounds requires adequate con— striction of both the oral and nasal ports so that air can be held under pressure in the mouth and then released. Although there is information presently available concerning the probable degree of velopharyngeal closure necessary (1 , .9, 10), the influence of oral port constriction on respiratory parameters associated with speech has been neglected. In light of evidence revealing a higher incidence of fricative articula-tion deficits in cleft palate speakers compared to plosive errors (5, 6', 7) , it is important to consider the possibility that, by its influence on pressure and airflow in the mouth and nose, oral port function may be partly responsible for the observed differences in consonant intelligibility. Since constriction of the oral port involves complex interaction of such structures as the tongue, lips, teeth, and anterior palate, it is diflicult to evaluate oral cavity dimensions during speech. Techniques such as cineradiography, cephalometrics, and manometrics cannot delineate struc— tural relationships well enough for this determination. In this investigation, therefore, a simple mechanical model of the upper speech mechanism was utilized to evaluate effects of oral constriction on the respiratory aspects of speech. Briefly, it was assumed that if a model could be designed to adequately simulate the physiological parameters of speech, then data obtained from it could be viewed with a fair degree of confidence and could possibly provide a better understand— ing of the phenomenon of 'cleft palate' speech. The following questions were considered: a) assuming that the laws of hydraulics apply to pressure-flow relationships during speech, how closely can the respiratory patterns of normal and cleft palate speech be copied by a model, and b) what are the effects of oral port size on pressure—flow relationships in the upper pharynx?