<P> Neurons sensitive to inter-aural level differences (ILDs) are excited by stimulation of one ear and inhibited by stimulation of the other ear, such that the response magnitude of the cell depends on the relative strengths of the two inputs, which in turn, depends on the sound intensities at the ears . </P> <P> In the auditory midbrain nucleus, the inferior colliculus (IC), many ILD sensitive neurons have response functions that decline steeply from maximum to zero spikes as a function of ILD . However, there are also many neurons with much more shallow response functions that do not decline to zero spikes . </P> <P> Most mammals are adept at resolving the location of a sound source using interaural time differences and interaural level differences . However, no such time or level differences exist for sounds originating along the circumference of circular conical slices, where the cone's axis lies along the line between the two ears . </P> <P> Consequently, sound waves originating at any point along a given circumference slant height will have ambiguous perceptual coordinates . That is to say, the listener will be incapable of determining whether the sound originated from the back, front, top, bottom or anywhere else along the circumference at the base of a cone at any given distance from the ear . Of course, the importance of these ambiguities are vanishingly small for sound sources very close to or very far away from the subject, but it is these intermediate distances that are most important in terms of fitness . </P>

When will a sound be in the cone of confusion