Phoneme recognition and confusions with multichannel cochlear implants: consonants.

The aim of this study was to investigate how postlingually severely or profoundly hearing-impaired adults relearn to recognize consonants after receiving multichannel cochlear implants. Consonant recognition of 19 Finnish-speaking subjects was studied for a minimum of 6 months and a maximum of 24 months using an open-set nonsense-syllable test in a prospective repeated-measure design. Responses were coded for phoneme errors, and proportions of correct responses and 95% confidence intervals were calculated for recognition and confusions. Two years after the switch-on, the mean recognition of consonants was 71% (95% confidence interval = 68-73%). The manner of articulation was easier to classify than the place of articulation, and the consonants [s], [r], [k], [t], [p], [n], and [j] were easier to recognize than [h], [m], [l], and [v]. Adaptation to electrical hearing with a multichannel cochlear implant was successful, but consonants with alveolar, palatal, or velar transitions (high F2) were better recognized than consonants with labial transitions (low F2). The locus of the F2 transitions of the consonants with better recognition was at the frequencies 1.5-2 kHz, whereas the locus of the F2 transitions of the consonants with poorer recognition was at 1.2-1.4 kHz. A tendency to confuse consonants with the closest consonant with higher F2 transition was also noted.