Localization cues of sound sources in the upper hemisphere.

The results of two localization tests of sound sources support our hypothesis that if a direction of a sound source in the upper hemisphere is expressed by two angles α and β, instead of the azimuth angle ψ and the elevation angle θ, the localization accuracy can be explained by two mutually independent cues. One is a binaural disparity cue which determines the angle α, and the other is a spectral cue which determines the angle β. The angle α is the angle between the aural axis and a straight line connecting a sound source with the center of a subject's head. The angle β is the angle between the horizontal plane and the perpendicular from a sound source to the aural axis. The data indicate that the “directional band” shown by Blauert can occur in any plane parallel to the median plane.