Binaural fusion and mis-identification of spatially separated concurrent vowels by cochlear implant users.

Excess binaural fusion can be problematic for listeners in noisy environments, leading to fusion of speech from multiple talkers. Previous research found that hearing aid users experience broad binaural fusion, fusing concurrent dichotic vowels with voice pitch differences of up to an octave [Reiss and Molis (2021) J. Assoc. Res. Otolaryngol. 22(4), 443-461]. This study examined whether cochlear implant (CI) users, compared to normal-hearing listeners, also exhibit abnormal fusion of concurrent double vowels in free-field conditions. The results revealed that CI users often fuse and mis-identify vowels even with large pitch differences, suggesting that they face additional challenges in noisy environments due to excessive binaural fusion.