I was always told that the reason we had two ears, and only one mouth ws that we were supposed to listen twice as much as we ought speak. This said, I started speaking late in life, although once I started, never really stopped.

In response to sound waves reaching both ears simultaneously, it is not exclusive to immediately in front of and behind... There is a full circle of indeterminacy that could be said to "rotate" the X-axis of our heads, thusly "travelling" from our feet, out in front of us, to above our heads, to behind us, and back to the feet. For this reason, when they set up sound systems for special effects in theatres, they give little attention to how high a sound effect is to be. Bird noises may come from ground level, with little notice from the audience. But woe to the techie that allows a Stage Left phone to ring from Stage Right.

In case the point has not been sufficiently overstated, if one was to place five columns of five speakers on a stage, the "left-right" sound could be determined easily, but to have the same ease in determining the "up-down"ness of the sound, one would have to rotate one's head on the Z-axis (cock their head to either side).