Auditory spectral discrimination and the localization of clicks in the sagittal plane.

Experiments show that the ability of human listeners to localize an impulsive sound in the medial sagittal plane (front, overhead, rear) deteriorates as the level of the sound increases. This negative level effect is strong for clicks but does not appear for broadband noise. It is conjectured that the negative level effect arises because the tonotopic excitation pattern is broadened for intense impulsive sounds. As a result, the spectral peaks and valleys, which are caused by anatomical filtering and which normally code for localization in the sagittal plane, are less recognizable. Filtered click discrimination experiments using headphones also show a negative level effect for clicks, but not for noise, and support this conjecture.