The effect of eye position and background noise on vertical sound localization

The influence of the eye position in combination with a simultaneously presented background (frame) sound on the auditory localization of a single (target) sound source was investigated in the median vertical plane (MVP). Five loudspeakers ranged from -20 degrees to +20 degrees with the center speaker at 0 degrees elevation. Listeners verbally estimated the position of a 500-ms noise stimulus, which was presented while they were fixating visual targets in various elevations. The perceived sound elevation appeared to be shifted 8.6 degrees on average towards the direction of eccentric gaze. When the target was temporarily embedded in a 2-s frame sound (emitted by one of the two outer loudspeakers) and the gaze was fixated at a straight-ahead position, the listeners consistently shifted the apparent target positions about 4 degrees away from the frame locations. This auditory contrast effect, which is consistent with earlier findings, remained even if the gaze direction deviated from straight ahead. It is concluded that the auditory contrast effect exists independently from the eye position effect and that the two effects act separately on auditory sound localization.