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Background and Aim: Nowadays, auditory perception is not a complete method to assess vowels quality and we need to use more objective instruments.In this study we want to determine and compare the persian vowels formants in normal and hearing Impaired students in 7ـ9 year old children of Isfahan.
Materials and Methods: This cross sectional study was performed on 64 normal and hearing impaired students. Background information was by interview and then, vowel production test was performed. First three formants of each vowel were obtained and recorded by speech studio soft ware and Dr. Speech device Data were compared between groups.
Results: Mean F₁ and F₂, and F₂/F₁ and F₃/F₁ ratio of Persian vowels between these three studied groups were different significantly. Mean F₃ of /o/, /e/ and /a/ in all groups was different significantly. Although we could not find such a significant differences for /u/, /i/ and /æ/ between these groups(p<0.05).
Conclusion: The most important difference between normal and hearing impaired children is their vowel Space, and we found that, the more sever the hearing impairment is, the closer vowel space will be seen. The hearing impaired children rely mostly on their proprioceptive sense because of their hearing deficiency and it causes less movement of the tongue, so they usually substitute vowels which have similar F₁ and F₂.

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Background and Aim: Formant structure and vowel space are the most important acoustic characteristics of speech sounds. The purpose of this study was to determine formant frequency and vowel space in six Persian vowels.
Methods: This cross-sectional descriptive-analytic study was performed on 60 Persian students of Tehran University of Medical Sciences (30 males, 30 females) with their age ranging from 18 to 24 years. The subject articulated six Persian vowels in isolation and data was recorded by real-analyzer software. Then, the first three formant frequency of each vowel was determined for each subject. Vowel formant frequency averages were measured separately for each vowel and each gender. Vowel space was plotted. The difference between F0 in two groups was compared by Leven and independent sample t tests.
Results: Maximum and minimum values of F0 in both group was related to /æ/ and /a/ (135 Hz in males and 239 Hz in females) and /i/ (146 Hz in males and 239 Hz in females). Besides, F0 in females was significantly higher than males (p<0.001). Maximum and minimum values of F1 were related to /æ/ and /i/. Furthermore, maximum and minimum values of F2 were related to /i/ and /u/. Maximum and minimum values of F3 were related to /i/ and /u/.
Conclusion: The lowest vowels were /æ/ and /a/ and the highest was /i/. The frontest was /i/ and the backest was /u/. the spreadest vowel was /i/ and the roundest was /u/.

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Background and Aim : Nasalization of a vowel refers to the addition of nasal resonance to the vocal tract transfer function. Also, vowel nasalization occurs because of coarticulation. Coupling of the nasal resonating space to the oropharyngeal cavity alters the vocal tract formants in complex ways. The purpose of this study was to investigate the effect of nasalization on /a/ vowel formants in before and after nasal consonant.

Methods: In current cross-sectional study, voice samples of 60 normal children ranging the age of four-nine years were investigated. Participants were asked to repeat / ʔ ama/ three times and vowel /a/ after presentation of an auditory model. Then, obtained samples were analyzed using Praat 5.3.13 . Average of F₀, F₁, F₂ and F₃ were calculated for /a/ comes before and after /m/ in production of / ʔ ama/ over three trials.

Results: There were statistically significant differences of F₁, F₂ and F₃ between / a/ which proceeds nasal consonant and /a/ follows nasal consonant , the before nasal consonant /a/ versus single /a/ and the after nasal consonant /a/ versus single /a/ (p=0.001 for all).

Conclusion : F₁, F₂ and F₃ in /a/ before nasal consonant affected by anticipatory nasal coarticulation and in /a/ after nasal consonant affected by carry-over nasal coarticulation . This study showed nasal coarticulation and nasalization result in decreasing F₁, F₂ and F₃ in /a/ vowel.