Intelligibility of vowels produced by post-lingually deafened cochlear implant users

The present study addresses the effect of cochlear implantation on the inte lligibility of vowels produced by 20 post-lingually deafened Dutch subjects . All subjects received the Nucleus-22 cochlear implant (3 WSP and 17 MSP p rocessors). Speech recordings were made pre-implantation and three and twel ve months pest-implantation with the implant switched on and off. Vowel int elligibility (monophthongs only) was determined using a panel of listeners. For all implanted subjects intelligibility was measured in a noisy backgro und. For seven poorly speaking subjects it was also measured in a quiet bac kground. After implantation with the Nucleus-22 device the results showed that vowel intelligibility, measured for all subjects in a noisy background, increase d for most of them (about 15), while it increased for about half the number of poorly speaking subjects measured in a quiet background. Twelve months after implantation vowel intelligibility, measured for all subjects in nois e, appeared to be based on first and second formant information. This was a lso found for the subgroup of seven subjects performing poorly pre-implanta tion when analysed separately. However, vowel intelligibility for this subg roup, when measured in a quiet background, was based also on vowel duration . The differences between the overall result in noise and the results of th e subgroup in quiet should be attributed mainly to the noise and not to asp ects of poor speech production in the subgroup. In addition, this study addresses the relationship between the intelligibil ity scores and objective measurements of vowel quality performed in a previ ous study.(1) The results showed that the vowel intelligibility scores are mainly determined by the position of the second formant frequencies.