Hearing impairment and vowel production. A comparison between normally hearing, hearing-aided and cochlear implanted Dutch children

• Hearing-impaired children reduce their vowel formant values.
• Hearing-impaired children have a significantly smaller vowel space.
• Hearing-impaired children show a smaller vowel differentiation.
• There is little difference between cochlear implant and hearing aided children.

This study investigated the acoustic characteristics of the Belgian Standard Dutch vowels in children with hearing impairment and in children with normal hearing. In a balanced experimental design, the 12 vowels of Belgian Standard Dutch were recorded in three groups of children: a group of children with normal hearing, a group with a conventional hearing aid and a group with a cochlear implant. The formants, the surface area of the vowel space and the acoustic differentiation between the vowels were determined. The analyses revealed that many of the vowels in hearing-impaired children showed a reduction of the formant values. This reduction was particularly significant with respect to F2. The size of the vowel space was significantly smaller in the hearing-impaired children. Finally, a smaller acoustic differentiation between the vowels was observed in children with hearing impairment. The results show that even after 5 years of device use, the acoustic characteristics of the vowels in hearing-assisted children remain significantly different as compared to their NH peers.