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Background and Aim: There are evidences that indicate a relationship between auditory processing disorders and stuttering, and any disorder in the central auditory function can be at least one of the underlying causes of stuttering. Even though, using the most state of the art radiographic technologies, i.e. MRI, no definitive answer has been given in relative to this question. In this research, using Mask-ing Level Difference (MLD) and Synthetic Sentence Identification (SSI) tests, the central auditory function of stutters and normal group was evaluated.
Materials and Methods: In this study was analytic cross-sectional, fifteen male patients with stutter-ing and 15 male normal cases with the age range from 16 to 40 years (average age 26.78 year) were evaluated. SSI-ICM, SSI-CCM and MLD tests were performed. The results were compared in both groups.
Results: Although stutterers mean MLD was less than that of normal group, the different was not significant between stutters and normal group in SSI test in right ear at negative MCRs. There was a significant difference in ICM state, but in CCM state, there was no significant difference between the average score of two groups in various MCRs.
Conclusion: The findings of this research is compatible with those of similar researches about the SSI test and the pattern of results, probably indicates a partial dysfunction of brainstem in some of the stutters.

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Background and Aim: One of the chemical pollutions which is frequently common in industry-other than noise is carbon monoxide. The present study aimed to assess the putative protective effect of N-acetylcysteine on the function of outer hair cells of rabbits exposed simultaneously to noise and carbon monoxide.
Methods: 24 male rabbits are entered in this interventional study. After obtaining baseline distortion product otoacoustic emissions, rabits were randomely devided into four groups. The groups Included: exposed with noise and received saline, exposed with noise and carbon monoxide and received saline, exposed with noise and received N-acetylcysteine, and exposed with noise and carbon monoxide and received N-acetylcysteine. Subsequently, they were evaluated again with distortion product otoacoustic emissions in two stages (two hours and one week after the exposure). Data were recorded and analyzed using paired and independent sample t-tests.
Results: Exposure to noise, and also simultaneous exposure to noise and carbon monoxide, and moreover using N-acetylcysteine in both groups, produced significant changes in distortion product otoacoustic emissions amplitudes (p<0.005).
Conclusion: The findings of the present research reveal that simultaneous exposure to noise and carbon monoxide may potentiate noise induced hearing loss. In addition, utilizing N-acetylcysteine can be used as a preventive agent for noise induced hearing loss and to avoid its potentiation with carbon monoxide.

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Background and Aim: Recently, researchers have increasingly turned to study the relation between stuttering and syntactic complexity. This study investigates the effect of syntactic complexity on the amount of speech dysfluency in stuttering Persian-speaking children and adults in conversational speech. The obtained results can pave the way to a better understanding of stuttering in children and adults, and finding more appropriate treatments.
Methods: In this cross-sectional study, the participants were 15 stuttering adult Persian-speakers, older than 15 years, and 15 stuttering child Persian-speakers of 4-6 years of age. In this study, first a 30 minute sample of the spontaneous speech of the participants was provided. Then the utterances of each person were studied in respect to the amount of dysfluency and syntactic complexity. The obtained information was analyzed using paired samples t-test.
Results: In both groups of stuttering children and adults, there was a significant difference between the amount of dysfluency of simple and complex sentences (p<0.05).
Conclusion: The results of this study showed that an increase in syntactic complexity in conversational speech, increased the amount of dysfluency in stuttering children and adults. Moreover, as a result of increase of syntactic complexity, dysfluency had a greater increase in stuttering children than stuttering adults.

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Background and Aim: Behavioral audiometry is the best method of hearing evaluation. Hearing thresholds are estimated with auditory evoked responses in patients who are not able to cooperate in behavioral audiometry. Because rehabilitative decisions are based on behavioral thresholds, it is essential to determine the amount of difference between behavioral and evoked response thresholds. The purpose of this study was to evaluate the difference between functional and auditory steady-state response (ASSR) gains.

Methods: Twenty six moderate to severe hearing impaired adolescents and adults (age range: 14 to 55 years) participated in this interventional-comparative study. Audiometery and ASSR testing was performed (without hearing aid and then with hearing aid). Finally, functional gain with ASSR gain, and behavioral thresholds with ASSR thresholds were compared using paired t-test and correlation statistical methods. All tests were performed in the sound field.

Results: The mean difference was 6.19 dB between unaided behavioral and ASSR thresholds, 4.33 dB between aided thresholds, and 2.43 dB between functional and ASSR gains. There was no significant difference between functional and ASSR gains (p>0.05).

Conclusion: The difference between functional and ASSR gains is less than the difference between behavioral and ASSR thresholds and it has less variability between different frequencies. So, it may be better to use ASSR gain instead of ASSR thresholds in hearing aid fitting in difficult-to-test population.

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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.