The effect of partially restored hearing on speech production of postlingually deafened adults with multichannel cochlear implants.

The effect of auditory feedback on speech production was investigated in five postlingually deafened adults implanted with the 22-channel Nucleus device. Changes in speech production were measured before implant and 1, 6, and 24 months postimplant. Acoustic measurements included: F1 and F2 of vowels in word-in-isolation and word-in-sentence context, voice-onset-time (VOT), spectral range of sibilants, fundamental frequency (F0) of word-in-isolation and word-in-sentence context, and word and sentence duration. Perceptual ratings of speech quality were done by ten listeners. The significant changes after cochlear implantation included: a decrease of F0, word and sentence duration, and F1 values, and an increase of voiced plosives' voicing lead (from positive to negative VOT values) and fricatives' spectral range. Significant changes occurred until 2 years postimplant when most measured values fell within Hebrew norms. Listeners were found to be sensitive to the acoustic changes in the speech from preimplant to 1, 6, and 24 months postimplant. Results suggest that when hearing is restored in postlingually deafened adults, calibration of speech is not immediate and occurs over time depending on the age-at-onset of deafness, years of deafness, and perception skills. The results also concur with hypothesis that the observed changes of some speech parameters are an indirect consequence of intentional changes in other articulatory parameters.