A comparison of different binaural hearing aid systems for sound localization in the horizontal and vertical planes.

Three groups of hearing-impaired listeners who had been fitted binaurally with behind-the-ear (BTE), in-the-ear (ITE), or in-the-ear-canal (ITC) hearing aids were tested on spatial localization function for sources in the frontal horizontal and vertical planes. No significant differences in unaided performance were observed between the groups, nor between that and aided performance in the BTE and ITE wearers. ITC wearers, by contrast, showed a deterioration in aided over unaided performance. From observations of performance when each group wore temporary fittings of the other two types of system, and from the performance of a non-impaired control group, it appears that the performance decrement for the ITC wearers was due to their own particular systems although specific reasons for this decrement could not be identified. In all conditions, aided and unaided, vertical plane localization was markedly disrupted in all the hearing impaired groups. It was also disrupted, to a lesser but still substantial extent, in aided conditions for the non-impaired listeners.