I’ve given this subject some attention in the past. It seems to be a fact, that as long as a sound stream is temporally complex, Humans can use the Inter-Aural Delay, as one of several hints as to the direction, which the sound came from. But as soon as the sound is temporally uniform, we cannot.
The way I’d explain this is without physical controversy. The way neurons fire, they can either be seen to carry binary or analog information. In short, one firing of a neuron could be like a ‘1’ as opposed to a ‘0’. Or, the steady rate at which a different type of neuron is firing, could encode an analog level. Well, some neurons seem to operate in both modes. At the onset of a signal, they could fire a short burst, after which a steady rate indicates a sustained amplitude.
The length of the path, which signals from the left auditory nerve need to take, to reach the left auditory cortex, may be exactly the same, as the length of the path, with which signals from the right auditory nerve take, to reach the left auditory cortex.
Therefore, the auditory cortex should be in a good position to discern in which order pulses of sound, or onsets of sound, reach it, as part of its information to determine direction, hence, to perceive the IAD.
But AFAICT, if the amplitude of a sine-wave is constant, then there is no real way in which our cortex can discern in what relative phase position it has reached our two ears.
(Updated 11/22/2018, 18h55 … )