Purpose: This study assessed the intelligibility of obstruent consonants in prelingually deafened Mandarin-speaking children with cochlear implants (CIs).
Method: Twenty-two Mandarin-speaking children with normal hearing (NH) aged 3.25-10.0 years and 35 Mandarin-speaking children with CIs aged 3.77-15.0 years were recruited to produce a list of Mandarin words composed of 17 word-initial obstruent consonants in different vowel contexts. The children with CIs were assigned to chronological age-matched (CA) and hearing age-matched (HA) subgroups with reference to the NH controls. One hundred naïve NH adult listeners were recruited for a consonant identification task that consisted of a total of 2,663 stimulus tokens through an online research platform. For each child speaker, the consonant productions were judged by seven to 12 different adult listeners. An average percentage of consonants correct was calculated across all listeners for each consonant.
Results: The CI children in both the CA and HA subgroups showed lower intelligibility in their consonant productions than the NH controls. Among the 17 obstruents, both CI subgroups showed higher intelligibility for stops, but they demonstrated major problems with the sibilant fricatives and affricates and showed a different confusion pattern from the NH controls on these sibilants. Of the three places (alveolar, alveolopalatal, and retroflex) in Mandarin sibilants, both CI subgroups showed the lowest intelligibility and the greatest difficulties with alveolar sounds. For the NH children, there was a significant positive relationship between overall consonant intelligibility and chronological age. For the children with CIs, the best fit regression model revealed significant effects of chronological age and age at implantation, with their quadratic terms included.
Conclusions: Mandarin-speaking children with CIs experience major challenges in the three-way place contrasts of sibilant sounds in consonant production. Chronological age and the combined effect of CI-related time variables play important roles in the development of obstruent consonants in the CI children.