Spatial Discrimination of Sound Sources in the Median Plane: The Effect of a Preceding Noise

The effect of a preceding noise on the spatial discrimination of two subsequent, successively presented target sounds was tested in the median plane. Subjects judged the vertical position of the second target sound relative to the first in a two-alternative forced- choice paradigm. The first target sound was randomly presented either at the same position as a preceding 3-s noise or at a different position. In comparison with a control condition, in which no noise preceded, the spatial discrimination of the second target was improved in the first condition, but was worsened in the second. An additionally presented visual stimulus that acted as a spatial cue to the target position had no significant influence on performance. The improvement in discrimination is consistent with earlier findings in sound lateralization. It may be associated with an auditory contrast effect recently reported for vertical sound localization.