Bilateral versus unilateral cochlear implantation in adult listeners: speech-on-speech masking and multitalker localization

Baljeet Rana, Jörg M. Buchholz, Catherine Morgan, Mridula Sharma, Tobias Weller, Shivali Appaiah Konganda, Kyoko Shirai, Atsushi Kawano

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    12 Citations (Scopus)
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    Binaural hearing helps normal-hearing listeners localize sound sources and understand speech in noise. However, it is not fully understood how far this is the case for bilateral cochlear implant (CI) users. To determine the potential benefits of bilateral over unilateral CIs, speech comprehension thresholds (SCTs) were measured in seven Japanese bilateral CI recipients using Helen test sentences (translated into Japanese) in a two-talker speech interferer presented from the front (co-located with the target speech), ipsilateral to the first-implanted ear (at +90° or -90°), and spatially symmetric at ±90°. Spatial release from masking was calculated as the difference between co-located and spatially separated SCTs. Localization was assessed in the horizontal plane by presenting either male or female speech or both simultaneously. All measurements were performed bilaterally and unilaterally (with the first implanted ear) inside a loudspeaker array. Both SCTs and spatial release from masking were improved with bilateral CIs, demonstrating mean bilateral benefits of 7.5 dB in spatially asymmetric and 3 dB in spatially symmetric speech mixture. Localization performance varied strongly between subjects but was clearly improved with bilateral over unilateral CIs with the mean localization error reduced by 27°. Surprisingly, adding a second talker had only a negligible effect on localization.

    Original languageEnglish
    Pages (from-to)1–15
    Number of pages15
    JournalTrends in Hearing
    Publication statusPublished - 1 Jan 2017

    Bibliographical note

    Copyright the Author(s) 2017. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


    • spatial release from masking
    • better-ear glimpsing
    • localization
    • cochlear implants
    • bilateral benefit

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