Sound Localization in Unilateral Cochlear Implant Users

Abstract

Purpose: Sound is localized by two ears. People with bilaterally severe-to-profound hearing loss may struggle to identify the direction of a sound if their hearing device delivers sound only one ear due to the loss of binaural advantage. The purpose of this study was to systematically investigate the sound localization performance of people with unilateral cochlear implant users. Methods: Ten unilateral cochlear implant users and 10 normal hearing adults participated in this study. Sound localization tests were conducted using five stimuli (speech, speech with noise, 500 Hz warble tone, 1 kHz warble tone, and 4 kHz warble tone) presented from eight loud-speakers. Correct responses and root-mean-square errors were obtained to investigate the localization performances and error patterns. Additional factors including the Korean-Speech Spatial and Qualities of Hearing Questionnaire were also analyzed. Results: Localization performance was significantly poor in the unilateral cochlear implant group showing polar patterns toward their hearing side. While the normal hearing group showed better localization for speech in quiet conditions compared to 500 Hz warble tone, the cochlear implant group did not show any statistical difference in performance across the stimuli due to their very poor performance. The Korean-Speech Spatial and Qualities of Hearing Questionnaire was associated with localization performance in limited conditions. Conclusion: The present study revealed that unilateral cochlear implant users correctly localize a sound at nearly chance levels. The Korean-Speech Spatial and Qualities of Hearing Questionnaire predict localization performance for unilateral cochlear implant users only for particular conditions.