IMPROVING CONSONANT INTELLIGIBILITY FOR INERAID PATIENTS FIT WITH CONTINUOUS INTERLEAVED SAMPLING (CIS) PROCESSORS BY ENHANCING CONTRAST AMONG CHANNEL OUTPUTS

Objective: In Experiment 1 the objective was to determine whether pati ents who have been implanted with the Ineraid electrode array perform better on tests of consonant identification when signals are processed through a continuous interleaved sampling (CLS) processor than when s ignals are processed through an analogue (Ineraid) processor. In Exper iment 2 the objective was to determine, for patients using the CIS str ategy, whether identification accuracy for stop consonant place of art iculation could be improved by enhancing differences in the patterns o f the signal processor channel outputs. Design: In Experiment 1, 16 co nsonants were presented in VCV format for identification. In Experimen t 1 the CIS patients evidenced difficulty in identifying /p t k/. Ther efore, in Experiment 2 the voiceless stop consonants were presented in two stimulus conditions. In one, the stimuli were unfiltered In the o ther, the stimuli were individually filtered so as to enhance the diff erences in channel outputs for /p/, /t/, and /k/. Results: In Experime nt 1 the patients performed better with CIS processors than with analo gue processors. In Experiment 2 the ''enhanced' stimuli were identifie d with better accuracy than were the unfiltered stimuli. Conclusions: We confirm that Ineraid patients achieve higher scores on tests of con sonant identification when using a CLS processor than when using an an alogue processor. Errors in identification of stop consonant place of articulation, when using a CIS processor, are due to the similarity in the patterns of the processor's channel outputs. By showing that cons onant intelligibility can be improved by filtering, we show that we ha ve not reached the limit of speech understanding that can be supported by the population of neural elements remaining in our patients' audit ory systems.