Cochlear Place of Stimulation Is One Determinant of Cochlear Implant Sound Quality.

OBJECTIVE: Our aim was to determine the effect of acute changes in cochlear place of stimulation on cochlear implant (CI) sound quality. DESIGN: In Experiment 1, 5 single-sided deaf (SSD) listeners fitted with a long (28-mm) electrode array were tested. Basal shifts in place of stimulation were implemented by turning off the most apical electrodes and reassigning the filters to more basal electrodes. In Experiment 2, 2 SSD patients fitted with a shorter (16.5-mm) electrode array were tested. Both basal and apical shifts in place of stimulation were implemented. The apical shifts were accomplished by current steering and creating a virtual place of stimulation more apical that that of the most apical electrode. RESULTS: Listeners matched basal shifts by shifting, in the normal-hearing ear, the overall spectrum up in frequency and/or increasing voice pitch (F0). Listeners matched apical shifts by shifting down the overall frequency spectrum in the normal-hearing ear. CONCLUSION: One factor determining CI voice quality is the location of stimulation along the cochlear partition.

The Value of Unilateral CIs, CI-CROS and Bilateral CIs, with and without Beamformer Microphones, for Speech Understanding in a Simulation of a Restaurant Environment.

OBJECTIVE: Our primary aim was to determine, in a simulation of a crowded restaurant, the value to speech understanding of (i) a unilateral cochlear implant (CI), (ii) a CI plus CROS (contralateral routing of signals) aid system and (iii) bilateral CIs when tested with and without beamforming microphones. DESIGN: The listeners were 7 CI listeners who had used bilateral CIs for an average of 9 years. The listeners were tested with three device configurations (bilateral CI, unilateral CI + CROS, and unilateral CI), two signal processing conditions (without and with beamformers) and with speech either from +90°, -90°, or from the front. Speech understanding scores for the TIMIT sentences were obtained in the 8-loudspeaker R-SPACETM test environment - an environment which simulates listening in a crowded restaurant. RESULTS: In the unilateral condition, speech understanding, relative to speech directed to the CI ear, fell by 17% when speech was from the front and fell 28% when speech was to the side opposite the CI. These deficits were overcome with both CI-CROS and bilateral CIs, and scores for the two devices did not differ significantly for any location of speech input. Beamformer microphones improved speech understanding for speech from the front and depressed speech understanding for speech from the sides for all device configurations. Patients with bilateral CIs and beamformers achieved slightly, but significantly, higher scores for speech from the front than patients with CI-CROS and beamformers. CONCLUSIONS: CI-CROS is a valuable addition to the hardware options available to patients fit with a single CI. For patients fit with bilateral CIs, bilateral beamformers are a valuable addition in the condition of speech coming from in front of the listener. The small differences in performance in the CI-CROS and bilateral CI conditions suggest that patient preference for bilateral CIs is based largely on factors other than speech understanding in noise.