Simultaneous Measurements of Vowels Produced by a Hearing-Impaired Speaker

Perceptual judgments, acoustic measurements and electromyographic (EMG) records were obtained for one deaf speaker producing the vowels [i, I, æ, a, u, u] in an [hVd] frame. Overall listener judgments were consistent with spectral measurements. In general, front vowels were perceived as more similar to targets than back vowels, and high vowels were perceived correctly more often than low vowels. Experienced and inexperienced listeners were found to differ significantly in their categorization of the point vowels [i, æ, a, and u] but not for [I and u] . The vowel space, as determined by the formant frequency measures, was reduced with respect to normal values particularly in the region appropriate to high back vowels. However, EMG records of genioglossus and orbicularis oris do not entirely account for the perceptual and acoustic data. In particular, genioglossus activity is relatively undifferentiated across all vowels when compared to data from normals. The results of this study generally support the widespread notion of reduced vowel space secondary to a reduced range of tongue movement in this deaf speaker. The physiological records were also characterized by a significant degree of variability from token to token. In this regard, these data are different from acoustic and physiological patterns that have been previously reported for vowels produced by deaf speakers.