Objectives Listening to speech with multiple competing talkers requires the perceptual separation of the target voice from the interfering background. Normal-hearing (NH) listeners are able to take advantage of perceived differences in the spatial locations of competing sound sources to facilitate this process. Previous research suggests that bilateral (BI) cochlear-implant (CI) listeners cannot do so, and it is unknown whether single-sided deaf CI users (SSD-CI; one acoustic and one CI ear) have this ability. This study investigated whether providing a second ear via cochlear implantation can facilitate the perceptual separation of targets and interferers in a listening situation involving multiple competing talkers. Design BI-CI and SSD-CI listeners were required to identify speech from a target talker mixed with one or two interfering talkers. In the baseline monaural condition, the target speech and the interferers were presented to one of the CIs (for the BI-CI listeners) or to the acoustic ear (for the SSD-CI listeners). In the bilateral condition, the target was still presented to the first ear but the interferers were presented to both the target ear and the listener's second ear (always a CI), thereby testing whether CI listeners could use information about the interferer obtained from a second ear to facilitate perceptual separation of the target and interferer. Results Presenting a copy of the interfering signals to the second ear improved performance, up to 4-5 dB (12-18 percentage points), but the amount of improvement depended on the type of interferer. For BI-CI listeners, the improvement occurred mainly in conditions involving one interfering talker, regardless of gender. For SSD-CI listeners, the improvement occurred in conditions involving one or two interfering talkers of the same gender as the target. This interaction is consistent with the idea that the SSD-CI listeners had access to pitch cues in their NH ear to separate the opposite-gender target and interferers, while the BI-CI listeners did not. Conclusions These results suggest that a second auditory input via a CI can facilitate the perceptual separation of competing talkers in situations where monaural cues are insufficient to do so, thus partially restoring a key advantage of having two ears that was previously thought to be inaccessible to CI users.

Current clinical practice in programming a cochlear implant (CI) for individuals with single-sided deafness (SSD) is to maximize the transmission of speech information via the implant, with the implicit assumption that this will also result in improved spatial-hearing abilities. However, binaural sensitivity is reduced by interaural place-of-stimulation mismatch, a likely occurrence with a standard CI frequency-to-electrode allocation table (FAT). As a step toward reducing interaural mismatch, this study investigated whether a test of interaural-time-difference (ITD) discrimination could be used to estimate the acoustic frequency yielding the best place match for a given CI electrode. ITD-discrimination performance was measured by presenting 300-ms bursts of 100-pulses-per-second electrical pulse trains to a single CI electrode and band-limited pulse trains with variable carrier frequencies to the acoustic ear. Listeners discriminated between two reference intervals (four bursts each with constant ITD) and a moving target interval (four bursts with variable ITD). For 17 out of the 26 electrodes tested across eight listeners, the function describing the relationship between ITD-discrimination performance and carrier frequency had a discernable peak where listeners achieved 70% to 100% performance. On average, this peak occurred 1.15 octaves above the CI manufacturer’s default FAT. ITD discrimination shows promise as a method of estimating the cochlear place of stimulation for a given electrode, thereby providing information to optimize the FAT for SSD-CI listeners.

CIs provide listeners with unilateral deafness important benefits for speech perception in complex spatial environments, including a larger head-shadow benefit when speech and noise originate on opposite sides of the head, and an improved ability to perceptually organize an auditory scene with multiple competing voices.The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army/Navy/Air Force, Department of Defense, or US Government.

Cochlear implantation for this population of patients produced modestly improved localization accuracy, and most patients expressed satisfaction with this intervention. In this series of cochlear implantation after OHD, our first two patients had wound infection and dehiscence. We recommend perioperative and postoperative antibiotics to prevent this complication.

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