Combined effects of noise and reverberation on sound localization for listeners with normal hearing and bilateral cochlear implants

Purpose: This study examined the individual and combined effects of noise and reverberation on the ability of listeners with normal hearing (NH) and with bilateral cochlear implants (BCIs) to localize speech. Method: Six adults with BCIs and 10 with NH participated. All subjects completed a virtual localization test in quiet and at 0-, −4-, and −8-dB signal-to-noise ratios (SNRs) in simulated anechoic and reverberant (0.2-, 0.6-, and 0.9-s RT60) environments. BCI users were also tested at +8- and +4-dB SNR. A 3-word phrase was presented at 70 dB SPL from 9 simulated locations in the frontal horizontal plane (±90°), with the noise source at 0°. Results: BCIs users had significantly poorer localization than listeners with NH in all conditions. BCI users’ performance started to decrease at a higher SNR (+4 dB) and shorter RT60 (0.2 s) than listeners with NH (−4 dB and 0.6 s). The combination of noise and reverberation began to degrade localization of BCI users at a higher SNR and a shorter RT60 than listeners with NH. Conclusion: The clear effect of noise and reverberation on the performance of BCI users provides information that should be useful for refining cochlear implant processing strategies and developing cochlear implant rehabilitation plans to optimize binaural benefit for BCI users in everyday listening situations.