Differential-Rate Sound Processing for Cochlear Implants

The aim of this study was to evaluate the Differential-Rate Sound Processing (DRSP) strategy for speech perception by users of the Nucleus cochlear implant. The DRSP strategy uses both low and high rates of stimulation – applying a low rate of stimulation to apical, lower-frequency electrodes and a high rate of stimulation to basal, higher-frequency electrodes. Ten patients implanted with the Nucleus CI-24M cochlear implant were evaluated with three speech processing strategies: 250 pulses per second (pps) over all electrodes, 1500 pps over all electrodes, and DRSP with 250 pps on electrodes up to 2400 Hz and 1500 pps for the remaining electrodes. There was no difference found between strategies across research subjects for consonant, vowel, CVC words and sentences-in-noise tests. However, there were significant individual subject differences confirming that there is still a case for considering lowrate stimulation when Mapping patients. The DRSP strategy demonstrated a compromise between the fixed low-rate and high-rate strategies that can perform equal to or better than either of these strategies for most subjects.