Time-of-Arrival (TOA) Difference
This is the difference in arrival time of a sound at the two ears of the listener. It is probably the most important single factor in determining the direction of a sound. It is zero for sounds arriving from directly in front of the listener and is a maximum of about 0.6 ms (depending on the size of the head) for sounds arriving at 90° to the frontal axis. In general the TOA difference is proportional to sin θ in Figure 48.
Pure tones are generally very difficult, or even impossible, to locate ...