Purpose: Maximizing speech perception for cochlear implant (CI) users can be achieved by adjusting mapping parameters. The object of this study was to investigate optimal sets of parameters of stimulation rate and the number of maxima in the CI system. Methods: Listeners’ consonant and vowel perception was measured for different combinations of the number of maxima and stimulation rate using cochlear implant simulated stimuli. Twelve sets of speech stimuli were systematically created by changing the number of maxima and stimulus rate and were presented to 18 listeners with normal hearing. Results: The group mean percent correct scores indicated only two pairs of parameter combinations showed significantly different results. A rate of 1,800 pps and 6 maxima resulted in significantly better consonant performance compared to a rate of 500 pps and 20 maxima. In addition, the 900 pps/8 maxima condition was significantly better compared to 500 pps/20 maxima for the vowel test. Analysis of listeners’ confusion patterns revealed they were more likely to make perception errors for the consonants /ð/, /l/, and /r/ and for the vowels /∧/, /e/, /æ/, and /ɛ/. Information transmission analysis indicated that, among other features, the voicing feature was transmitted best for consonant recognition and the backness feature was the most transmitted for vowel recognition. Conclusions: The results of this study using vocoded speech with listeners with normal hearing contribute to a better understanding of CI users’ confusion patterns and possible ways to optimize cochlear implant signal processing strategies.
Purpose: Maximizing speech perception for cochlear implant (CI) users can be achieved by adjusting mapping parameters. The object of this study was to investigate optimal sets of parameters of stimulation rate and the number of maxima in the CI system. Methods: Listeners’ consonant and vowel perception was measured for different combinations of the number of maxima and stimulation rate using cochlear implant simulated stimuli. Twelve sets of speech stimuli were systematically created by changing the number of maxima and stimulus rate and were presented to 18 listeners with normal hearing. Results: The group mean percent correct scores indicated only two pairs of parameter combinations showed significantly different results. A rate of 1,800 pps and 6 maxima resulted in significantly better consonant performance compared to a rate of 500 pps and 20 maxima. In addition, the 900 pps/8 maxima condition was significantly better compared to 500 pps/20 maxima for the vowel test. Analysis of listeners’ confusion patterns revealed they were more likely to make perception errors for the consonants /ð/, /l/, and /r/ and for the vowels /∧/, /e/, /æ/, and /ɛ/. Information transmission analysis indicated that, among other features, the voicing feature was transmitted best for consonant recognition and the backness feature was the most transmitted for vowel recognition. Conclusions: The results of this study using vocoded speech with listeners with normal hearing contribute to a better understanding of CI users’ confusion patterns and possible ways to optimize cochlear implant signal processing strategies.
INTRODUCTION METHODS RESULTS DISCUSSION
