Background and Aim: Hearing loss results in impairment of  muscles coordination and survival essential that are engaged in motor speech timing tasks. It will negatively affect the acquisition of speech sounds. The purpose of this study was to compare the oral diadochokinesis in normal-hearing and hearing - impaired adolescents
Materials and Methods: This research was conducted on sixty-one adolescents aged 15-18 years old. Forty-six had moderately severe, severe, or profound hearing loss and fifteen were normal. The time spent to perform each oral diadochokinesis tasks was measured by speech analyzer of Dr. speech software, version four.
Results: Results indicated that hearing - impaired performed significantly slower on all speech timing tasks than their normal hearing peers except those with moderately severe hearing-impaired group. There were significant differences between profound hearing-impaired group and both other groups.
Conclusion: The results of this study point out  the motor speech problems in hearing impairment. The differences, in general, indicate that speech-timing coordination deficits are compromise with hearing loss degree.

Background and Aim: Children with speech and language disorders can have reduced diadochokinesis (DDK) rates. Although a relationship has been proposed between DDK and the rate of speech, there is no consensus among the experts and its credibility remains questioned. The purpose of this study was to compare oral DKK with the rate of speech and reading in normal students.

Methods: One hundred second grade female students participated in this descriptive-comparative study. The subjects were asked to read a text of their book, tell a story, and perform some oral DDK tasks. The elapsed time was measured by Cool Edit software. Descriptive statistics were used to describe the data. Data analysis was performed using Student t-test.

Results: Time history durations of DDK tasks /tâ/, /pâ/ and /kâ/ were 4.10, 4.15 and 4.74 ms, respectively. The rate of reading was 3.1 syllables per second and rate of talking was 2.8 syllables per second. No relationship between the rate of speech and DDK was found, still, we found a significant association between the reading rate and DDK in /kâ/ (p=0.03) and /pâtâkâ/ (P<0.01).

Conclusion: Relevant DDK tasks can be utilized in order to improve the reading rate. Reading rate was higher than speech rate and the rate of bilabial diadochokinesis in mono syllables is the highest rate that may be expected during the treatments.