There's one further aspect that has not been mentioned: the role of the
pinna (the external ear) in sound location.  It's not just to keep the
hat from sinking down over the eyes.  For more, check out
http://groups.yahoo.com/group/ultrasound/message/84?source=1

Also ask Google about "pinna sound location" (omit the quotes).

Here's another approach to perceived pitch:
http://jneuhoff.com/page12.htm

Peter Neilson