In Brief:
This study aimed to determine the number of stimulation channels needed for cochlear implant users to achieve asymptotic performance in the recognition of speech in noise. Performance in speech tests was measured for patients using the Med-El implementation of the CIS stimulation strategy with 2, 3, 4, 6, 8, and 10 channels out of a possible maximum of 12. Vowel, consonant, and sentence identification tests were presented against a background of pink noise to 11 subjects. Using moderate signal-to-noise ratios, asymptotic performance was achieved using 4 channels for consonants, 6 channels for vowels, and 8 channels for sentences. In another experiment, understanding of monosyllabic words reached a maximum value at a similar number of channels both in quiet and in pink noise, and the mean increase in test score between 6 and 11 channels (although statistically significant) was only 7%. The data suggest that 12 frequency channels are more than adequate for cochlear implant users to achieve asymptotic performance levels in clinical speech tests applied in the presence of wideband noise at moderate signal-to-noise ratios.
