Sound localisation of low- and high-frequency sounds in cochlear implant users with single-sided deafness

OBJECTIVE: Localisation of low- and high-frequency sounds in single-sided deaf cochlear implant users was investigated using noise stimuli designed to mitigate monaural localisation cues. DESIGN: Within subject design. Sound source localisation was tested in the horizontal plane using an array of seven loudspeakers along the azimuthal angle span from -90° to +90°. Stimuli were broadband noise and high- and low-frequency noise. STUDY SAMPLE: Twelve adult subjects with single-sided deafness participated in the study. All had normal hearing in the healthy ear and were supplied with a cochlear implant (CI) in their deaf ear. RESULTS: With broadband noise, the mean angular localisation error was 39° in aided condition as compared to a median angular error of 83.6° when the speech processor was not worn. For high-frequency noise, the median angular error was 30° and for low-frequency noise, it was 46° in the CI-aided condition. CONCLUSIONS: Single-sided deaf CI users show the best sound localisation for high-frequency sounds. This supports the view that interaural level differences are dominant for sound localisation in these listeners. Nonetheless, a limited ability to localise low-frequency sounds was observed, which may be based on the supportive perception of interaural time differences.