30 Mar 11, 10:42PM
(30 Mar 11, 06:37AM)V-Man Wrote: That raises the question...
With only two ears, can you really tell when a sound originates from behind or in front of (or above or below) you?
Short answer yes; the subtle filtering artifacts induced by ears themselves and especially the wave guides on the pinna, plus the very tiny delay in the soundwave reaching the "further" ear and the inevitable difference in the filtering characteristics between the 2 inputs... and some other details, like visual feedback reenforcing location perception - a centred sound without an apparent visual source is assumed to be behind you...
Echolocation isn't infallible though; a certain variety of frequencies must be present, or else we're literally clueless: in particular, higher frequencies (up to 12 kHz) are needed as the shorter wavelengths imply more phase information which is what we need - this is also why we can't locate deep bass properly (and you can put subwoofer almost anywhere, to an extent), wavelengths being too long.
Additionally, first reflections can confuse us: classic example being emergency sirens heard coming from the wrong side as we approach a junction, as the reflections off the street walls reach us far more clearly than the occluded source. Then as you get to the junction itself and clear both corners, the apparent source immediately switches to the other (source) side... on the plus side, if it's an ambulance, you'll be receiving qualified care immediately.