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Having access to the signals at the two ears is important for understanding speech in noisy conditions. One of the contributing mechanisms is better-ear glimpsing (BEG), which takes advantage of the fluctuating signal-to-noise ratios (SNRs) across ears. Even though the spatial benefit provided by bilateral (over unilateral) implantation has been studied widely, the benefit provided by BEG is still poorly understood. Therefore, speech comprehension performance was measured in ten bilateral CI users in a spatially-symmetric masker paradigm. Helen-like questions recorded with a female native English speaker were presented from a loudspeaker in front of the subject (0o) while two female speech distractors were presented either from loudspeakers at ±90o or co-located with the target questions. The subjects' task was to answer the questions. The combined distractor level was kept constant at 60 dBSPL and the level of the target questions was varied adaptively to obtain speech comprehension thresholds (SCTs), i.e., the SNR at which 50% of the questions were answered correctly. SCTs were measured unilaterally and bilaterally. The spatial benefit was calculated as the difference in SCTs between the spatially-separated and co-located condition for bilateral stimulation. The average benefit was 2 dB with individual results varying from -2 to 7 dB. The bilateral benefit was calculated as the difference in SCTs between bilateral and unilateral stimulation in the spatially- separated condition. The average bilateral benefit was 1.4 dB when compared to the better ear and 5.9 dB when compared to the worse ear. Individual results varied from -2.5 to 5 dB and 1.9 to 12.7 dB, respectively. Hence, bilateral CI users can benefit significantly from a second device in spatially-symmetric, fluctuating noise where neither of the ears receives a constant favorable SNR. Future research should further investigate the large inter-subject variability and further improve the observed benefits. [ABSTRACT FROM AUTHOR]

Auditory localization ability is commonly assessed in individual listeners by either asking them to identify the perceived direction of a stimulus or to discriminate the perceived direction of two stimuli presented successively. Here, a novel localization task is introduced that requires the subject to segregate as well as to localize two simultaneous talkers. This task is more challenging than common localization tasks and may address spatial auditory and cognitive processes that better reflect real world listening. Ten bilateral cochlear implant (CI) users were asked to localize short sentences spoken by either a single male or female talker or two simultaneously presented sentences spoken by a male and a female talker. The stimuli were presented randomly from 12 different directions at a sound pressure level of 60 dBSPL. Individual performance was measured for bilateral as well as for unilateral stimulation. Results revealed an average RMS localization error for unilateral stimulation of around 80 degees for both the single-talker and two-talker localization task, which basically reflected performance of guessing in all subjects. For bilateral stimulation, the average localization error reduced to 36 degrees for the single-talker localization task and to 55 degrees for the two-talker localization task. Bilateral results varied strongly across subjects, but showed a clear bilateral benefit for all subjects in the single-talker condition. The variation increased for the two-talker localization task, where some subjects showed similar performance as in the single-talker condition and others showed no bilateral benefit at all. The bilateral performance in the two-talker condition was significantly correlated with age, which may suggest that higher level processes are addressed such as spatial memory. Hence, the proposed two-talker localization task provides a promising method that may reflect spatial hearing outcomes with increased ecological relevance. [ABSTRACT FROM AUTHOR]