Vowel and diphthong production by young users of cochlear implants and the relationship between the phonetic level evaluation and spontaneous speech.

This investigation assessed how the vowel and diphthong production of young users of cochlear implants varied over time and how performance on the Phonetic Level Evaluation (PLE, Ling, 1976) corresponded with vowel and diphthong production during spontaneous speech. Eight children with prelingual deafness were tested with the PLE on five occasions: before receiving a Cochlear Corporation Nucleus cochlear implant and at the following points after receiving a cochlear implant: 6 months, 12 months, 18 months, and 24 or 36 months. An audiovideo recording of spontaneous speech was obtained at each test session. Performance on the PLE was scored with the scoring system designed by Kirk and Hill-Brown (1985). Performance during spontaneous speaking was scored by referencing a transcription of the spoken message to a transcription of the signed message. The correlations between the PLE and the spontaneous speech measures were weak, suggesting that performance on the PLE has low predictive value for vowel and diphthong production during spontaneous speaking. The results from the spontaneous speech samples collected over time suggest that two changes occurred: (a) vowel and diphthong production became more diverse and (b) production became more accurate. It is suggested that increased access to formant information enables subjects to enlarge their system of phonological performance and refine their motoric ability to establish vowel and diphthong targets.