Objective vocal parameters in Farsi-speaking adults with Down syndrome.

Previous studies have indicated significant differences in vocal parameters between children with Down syndrome and normal children. This study was performed to see whether there is a significant dissociation between normal adults and adults with Down syndrome in terms of some vocal parameters. The participants were 22 adults with Down syndrome and 22 normal adults matched for age and gender. We measured jitter, shimmer, fundamental frequency (F0), and maximum phonation time (MPT). The results showed a significantly higher F0 and a significantly lower jitter in the Down syndrome group compared to the control group, while the average amounts of MPT and shimmer were not different. Moreover, the shimmer and jitter of females in both groups were lower than those of males. These findings might be the result of a physiological retardation of the larynx rather than mental retardation in the Down syndrome population.

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.