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 (F1) and second formant frequency (F2) 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 F1 for vowel /i/ was significantly different (between CI and NH children and also between HA and NH groups) (F2, 57 = 9.229, P < 0.001). For vowel /a/, the mean value of F1 was significantly different (between HA and NH groups) (F2, 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). F2 for vowel /o/ was significantly different (F2, 57 = 4.572, P < 0.05). Also, the mean value of F2 for vowel /a/ was significantly different (F2, 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.