Better-ear glimpsing with symmetrically-placed interferers in bilateral cochlear implant users

Abstract

For a frontal speaker in spatially symmetrically placed maskers, normal hearing (NH) listeners can use an optimal “better-ear glimpsing” strategy selecting time-frequency segments with favorable signal-to-noise ratio in either ear. It was shown that for a monaural signal, obtained by an ideal monaural better-ear mask (IMBM), NH listeners can reach similar performance as in the binaural condition, but interaural phase differences at low frequencies can further improve performance. In principle, bilateral cochlear implant (BiCI) users could use a glimpsing strategy; however, they cannot exploit (temporal fine structure) interaural phase differences. Here, speech reception thresholds of NH and BiCI listeners were measured in two symmetric maskers (±60°; speech-shaped stationaty noise, non-sense speech, single talker) using head-related transfer functions and headphone presentation or direct stimulation in BiCI listeners. Furthermore, a statistically independent masker in each ear, diotic presentation with IMBM processing, and a noise vocoder based on the BiCI electrodogram was used in NH. Results indicate that NH with vocoder and BiCI listeners show a strongly reduced binaural benefit in the ±60° condition relative to the co-located condition when compared to NH. However, both groups greatly benefit from IMBM processing (as part of the CI stimulation strategy). Individual differences are compared.