Acoustic and perceptual evaluation of hypernasality of mentally retarded persons.

Acoustic and perceptual correlates of velopharyngeal competency in two groups of retarded (one Down syndrome, one idiopathic) and one group of nonretarded subjects, equally divided between males and females, was evaluated. There were 20 young adults in each group. Acoustic measures of hypernasality were obtained through analysis by TONAR II. Perceptual judgments were rendered by 15 listeners. Results of perceptual and acoustic analyses revealed that those persons with Down syndrome were significantly more hypernasal than were the other two groups. Those with idiopathic retardation were more hypernasal than were nonretarded subjects.