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Background and Aim: Human’s voice is observable and measurable like his other behaviours. Investigations have shown that characteristics of voice differ in males and females and possibly in different languages. Clinically, knowing natural voice characteristics is helpful for distinguishing voice pathologies. So the purpose of this study was to measure and compare the fundamental frequency human voice.

Materials and Methods: subjects were young males and females of Iranian Fars, Turk and Kurd races. First the subjects were asked to read some Persian sentences , then their voice samples were analysed by Dr.Speech software.

Results: Fundamental frequency mean is 168±46 Hz and 120±48 Hz for females and males , respectively , which shows significant difference. There is no significant difference between fundamental frequency mean of different races.

Conclusion: There is significant difference between fundamental frequency of males and females , but this difference is not attributable to their mother tongue. Key words: voice, fundamental frequency, Iranian, Fars , Turk , Kurd.

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Background and Aim: Objective measurement is general and acoustic measurements in particular have become a substantial aspect of stuttering assessment during the last few decades. Measurements do not replace the perceptual judgment, but they allow a more precise diagnosis, provide more evidence for therapeutic interventions, and are useful as feedback for patients in therapy. The purpose of this investigation was to compare some adult male stutterers&apos and nonstutterers&apos acoustic features.
Materials and Methods: Adult male stutterers and nonstutterers participated this case-control  study. Their fluent reading of 20 sentences in Farsi, prolongation of  vowels /a/ and /i/, and rhythmic counting from 1 to 20 were analyed with Dr. Speech software.
Results: There were no significant differences between two groups in fundamental frequency (f₀) and standard deviation of f₀ in three speech samples (vowels /a/ and /i/, reading 20 sentences, and rhythmic counting from 1 to 20). No significant difference were between two groups for jitter and shimmer.
Conclusion: Non significant differences between two groups are somewhat due to investigation of this parameters in fluent speech of stutterers  and nonstutterers.

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Backgrand and Aim: The measurement of speech intelligibility refer to determining the measure of speech intelligibility in communication. The speech intelligibility is used for decision-making in intervention, the determination of intervention goals, and the measurement of intervention outcomes. This study aimed to investigate the speech intelligibility among the children aged 36 to 60 months.

Methods: In this cross-sectional study, 360 healthy children (180 girls and 180 boys) were chosen among children of kindergardens in Khorramabad city, Iran. Speech sample of subjects was collected by calling pictures of Hydari et al 2010, speech intelligibility measurement test (2010). The voices of the subjects were tape-recorded and speech intelligibility of children was studied within 12 age-groups arranged by two months.

Results: The minimum speech intelligibility was concerned to 36 and 37 months old and the maximum was concerned to 58 and 59 months old. There was a significant differences among age-group 36 and 37 months old with 44 and 45 months old and above, age-group 38 and 39 months old with 55 and 54 months old and above, and age-group 40 and 41 months old with 58 and 59 months old (p<0.05 for all). There was no significant difference among other age groups. There was no significant difference between boys and girls.

Conclusion: Speech intelligibility has the highest growth during the age of 36 to 46 months and it had lowest growth during the age of 46 months and elder range.