Cephalometric and cineradiographic study of deviant resonance in hearing-impaired speakers

To study physiological basis for deviant resonance in hearing-impaired speakers, cephalometric roentgenography and cineradiography were applied to analyze oral/pharyngeal relationships during vowels produced in isolation and within a sentence context. The films, synchronized with sound recording, were traced and measured for 10 normal hearing and 4 hearing-impaired women with deviant resonance. Vocal tract conformations and dimensions were defined by measures of the lips, tongue, mandible, velum, hyoid bone, epiglottis, and laryngeal sinus. Means, standard deviations, and analyses of variance were applied to facilitate descriptions and comparisons between the groups. The hearing-impaired speakers had near normal lip openings for /i/ and /u/ but more open positions for /a/. The tongue tended to retract for the front vowel and front for the back vowel /u/. For high vowels, most of the hearing-impaired speakers had an elevated hyoid, an unusually large vertical dimension between hyoid and laryngeal sinus, and a retracted tongue root, which was associated with a marked retraction or deflection of the epiglottis toward the pharyngeal wall. The cine analysis of the normal hearing speakers showed rather well defined and consistent shifts in tongue position for the front vowels produced in the sentence context. The hearing-impaired speakers with deviant resonance showed greater variation among speakers in tongue body position and a significant retrusion of the dorsum of the tongue at a site significantly lower than observed in hearing speakers. The consistent tongue root retraction during static as well as dynamic speech production is interpreted as support for Boone's hypothesized cause of pharyngeal resonance in speech of the hearing impaired.