Role of two ears in upper hemisphere localization

It is well known that the elevation of a sound source is determined by spectral cues in the median plane, where the input signals to both ears are regarded as being identical. It is, however, still a problem how the elevation of a sound source is determined in any plane apart from the median plane, because the input signals to both ears are not identical. This paper investigates how the input signals to the left and right ears contribute to determine the elevation of a sound source at any position in the upper hemisphere. The localization tests regarding the elevation in five planes parallel to the median plane were performed. In the localization tests, pinna cavities of both or one of two ears were occluded. The results indicate that both ears play a role in determining the elevation of a sound source in any plane. Furthermore, they infer that the summation of spectral features of input signals to the left and right ears contributes to determine the elevation.