Acoustic Analysis of Persian Vowels in Cochlear Implant Users: A Comparison With Hearing-impaired Children Using Hearing Aid and Normal-hearing Children

Objective. Vowel production in essence is auditorily controlled; hence, the role of the auditory feedback in vowel production is very important. The purpose of this study was to compare formant frequencies and vowel space in Persian-speaking deaf children with cochlear implantation (CI), hearing-impaired children with hearing aid (HA), and their normal-hearing (NH) peers. Methods. A total of 40 prelingually children with hearing impairment and 20 NH groups participated in this study. Participants were native Persian speakers. The average of first formant frequency (F-1) and second formant frequency (F-2) of the six vowels were measured using Praat software (version 5.1.44). One-way analysis of variance (ANOVA) was used to analyze the differences between the three3 groups. Results. The mean value of F-1 for vowel/i/was significantly different (between CI and NH children and also between HA and NH groups) (F-2,F- 57 = 9.229, P < 0.001). For vowel /a/, the mean value of F-1 was significantly different (between HA and NH groups) (F-2,F- 57 = 3.707, P < 0.05). Regarding the second formant frequency, a post hoc Tukey test revealed that the differences were between HA and NH children (P < 0.05). F-2 for vowel /o/ was significantly different (F-2,F- 57 = 4.572, P < 0.05). Also, the mean value of F-2 for vowel /a/was significantly different (F-2,F- 57 = 3.184, P < 0.05). Conclusion. About 1 year after implantation, the formants shift closer to those of the NH listeners who tend to have more expanded vowel spaces than hearing-impaired listeners with hearing aids. Probably, this condition is because CI has a subtly positive impact on the place of articulation of vowels.