Document Type : Original Articles

Authors

• Ehsan Naderifar ¹
• Ali Ghorbani ²
• Negin Moradi ³
• Akbar Biglarian ⁴

¹ Health Promotion Research Center, Zahedan University of Medical Sciences, Zahedan, Iran

² Lecturer, Academic Member, Department of Speech Therapy, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran

³ Lecturer, Musculoskeletal Rehabilitation Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

⁴ Department of Biostatics, Academic Member, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran

Abstract

Introduction: Formant frequencies change as a function of articulatory movements and also of changes in the configuration of the vocal tract. Hearing-impaired people produce vowels with the limited vertical range and reduced arc of tongue which can lead to vowel formant centralization. The current study aimed at comparing formant frequencies of the vowels /a/, /i/and /u/ in children with varying degrees of hearing loss and their normal counterparts. Materials and Methods: The participants of this descriptive-analytic study were 80 normal and Hearing-impaired students (with moderate, moderate-to-severe, severe and profound degrees of hearing loss). The examinees were asked to produce the vowels /a/, /i/, /u/ for three times. The audio files were transferred to Praat software (version 13.3.5) for recording formants frequencies. One-way ANOVA followed by the post hoc test, Dunnett’s t, was applied for comparing the controls and subjects with hearing loss and the post hoc test, Duncan, was used for comparing the subgroups of hearing-impaired subjects. Results: Comparing the control and hearing-impaired groups, the F2 of vowels /a/ and /i/ had significant difference while the F1 of these vowels did not show any difference (considering F2a, the p values were as follows: control group- moderate group: P = 0.031, control group- moderate to severe group: P = 0.015, control group- severe group: P = 0.023, control group- profound group: P < 0.001 and considering F2i: control group- moderate group: P = 0.005, control group- moderate-to-severe group: P < 0.001, control group- severe group: P < 0.001, control group- profound group: P < 0.001). Among the subgroups of subjects with hearing loss, however, the F1u showed the largest differences. Conclusion: It was revealed that F2of vowels /a/, /i/ had greater ability for distinguishing abnormal from normal speech than the F2u and F1of /a/, /i/, /u/. It seems that the measuring F2of the vowels /a/ and /i/ can offer a new approach for faster and more accurate diagnosis and assessment of vowel impairments in hearing- impaired children. Keywords: Formant frequency, Hearing loss, Vowel