Objectives: One of the most effective methods to describe speech disorders is the measurement of speech intelligibility. The speech intelligibility indicates the extent of acoustic signals that correctly speaker produces and hearer receives. The purpose of this study was to investigate the speech intelligibility in the Persian children with Down syndrome; age range was 3 to 5 years, who had spoken Persian. Methods: This cross- sectional study investigates 12 children [6 girls and 6 boys] with Down syndrome who had referred to speech therapy clinic in Hamadan city and 12 normal children [6 girls and 6 boys] who went to the kindergarten in Hamadan city. The pictures of speech intelligibility test [in Persian language] were used to collect speech samples of participants. The participant’s voice was recorded by voice recorder and was investigated in two age groups.
Results: The results of this study indicated the means of speech intelligibility was 92.25 for normal children and 35.08 for children with Down syndrome. The correlation between age and speech intelligibility for normal children was 0.866 and for children with Down syndrome was 0.352. The mean of speech intelligibility 2 for normal boys was 93 and for normal girls 91.5 and for boys with Down syndrome 34.66 and for girls with Down syndrome 35.5.