Journal of Phonetics & Audiology
Open Access

Abstract

Effects of Reverberation on Sound Localization for Bilateral Cochlear Implant Users

Yunfang Zheng, Janet Koehnke and Joan Besing

The purpose of this study was to examine the effects of reverberation on the ability of listeners with bilateral cochlear implants (BCIs) to localize speech in anechoic and reverberant environments. Two specific research questions were addressed: (1) how do listeners with BCIs localize sounds in different environments compared to listeners with normal hearing (NH)? and (2) at what reverberation time (RT60) does localization performance begin to decline for both groups of subjects? Six adults with BCIs and ten with NH participated. All subjects completed a virtual localization test in simulated anechoic and reverberant environments (0.0, 0.2, 0.6, and 0.9 s RT60) in quiet. A three-word phrase was presented at 70 dBSPL from nine simulated source locations in the frontal-horizontal plane (± 900). Root-mean-square localization error (RMSLE) in degrees was calculated. Results revealed localization accuracy significantly decreased as reverberation time increased for both groups of subjects. Listeners with BCIs had significantly poorer localization accuracy than listeners with NH in all conditions. Their RMSLE changed from 320 in anechoic condition to 600 in RT60 0.9s condition, while corresponding change for listeners with NH was only from 170 to 220. In addition, localization performance of listeners with BCIs started to decrease at a shorter reverberation time (RT60 0.6s) compared to those with NH (RT60 0.9s). In conclusion, reverberation significantly degraded localization performance, with a greater influence on listeners with BCIs than listeners with NH. In addition, bilateral experience is likely to help listeners with BCIs achieve a better localization outcome over time. It is important to apply the information obtained in this study to optimize binaural benefit for listeners with BCIs in everyday listening situations.