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

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.

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.

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.

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.

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.