> "We hear in stereo 3-D." This is not true unless we move our heads. We hear in one dimension, left-to-right.

Put on some headphones and listen to this and tell me you cannot visualize it in 3-D:

http://www.youtube.com/watch?v=YuxaOO6PsAw

This is a binaural recording. More info on these here: http://en.wikipedia.org/wiki/Binaural_recording

You can hear in multiple dimensions because, as the original article mentions, there is some post-processing in your mind due to the time delay between sounds entering your left ear and sounds entering your right. Just because your ears are aligned on a single axis does not mean that you cannot perceive in multiple axes. No moving of your head is necessary to perceive in more than one dimension.