[An analytical study on recognition confusion of vowels in patients with 22 channel cochlear implant]

Vowel confusion was studied in 16 postlingually deaf patients with 22 multi-channel cochlear implants. Tests for vowel perception were performed on these patients after a 3 month training period, using/a,e,i,o,u/pronounced by a speech therapist. Analyses were conducted on the relationship between the vowel confusion matrix and the frequencies of the 1st and 2nd formants of vowels used in this study, and the relationship between the confusion matrix and the numbers in order of the activating electrodes. The results revealed that the higher percentages of errors in vowel recognition were as follows: /o/-->/a/ (12%),/o/-->/u/ (13%), and/e/-->/i/ (8%), possibly due to small differences found in the F1 and F2 frequency ratio or in the F2 frequency of the vowels, which results in a similar distance between two electrodes, pairs or similar stimulated places in the sense of the high frequency part of the cochlea.