Comparing tongue positioning by normal-hearing and hearing-impaired children during vowel production

Glossometric measures of tongue positions of 10 normal-hearing (NH) and 10 profoundly hearing-impaired (HI) children were compared during production of the eight vowels /i,I,E,ae,u,U,o,a/. The NH subjects used tongue positions with distinct vertical distances from the hard palate and discrete tongue shapes to distinguish the front vowels and the back vowels. The HI subjects produced vowels using a reduced vertical range and singular flat, high-back tongue shape. Token-to-token variability was greater for the HI subjects. Listener identifications of the vowels produced by the HI subjects fell in three categories: highly variable responses to /i/, low vowels for /I,E,ae,a/, and back vowels for /u,U,o/. The centralized, generally undifferentiated tongue positions and listener identifications for the HI subjects coincided with suppositions made from previous perceptual, acoustic, and physiologic findings.