Motor control of speaking rate and oral diadochokinesis in hearing-impaired Farsi speakers.

Although speech motor control has been studied intensively in normal-hearing and hearing-impaired (HI) speakers in America and Europe, essentially no research has been performed using Persian-speaking participants. A total of 46 prelingual hearing-impaired 15-18-year-old males and 15 normally hearing control participants from Iran participated in the study. Three speaking performance measures, oral diadochokinesis (DDK), speaking rate (words per minute), and intelligibility ratings, were obtained for the two groups and compared to previously published research for English-speaking participants. The DDK results in general showed that the normal-hearing group produced the fastest syllable rates, and the profoundly HI group produced the slowest. Similar results were obtained for speaking rates. Speech intelligibility was highest in the normal-hearing group and lowest in the profoundly HI group. Correlation analysis between DDK and speaking rates showed that for HI group only, a slow speaking rate corresponded to slow DDK rates. It is shown that generally there are significant differences in measures of speech motor control in normal-hearing and hearing-impaired participants. These results concord with those from other language groups.