At 12:20 PM 9/16/99 -0400, Harold wrote: >On Thu, 16 Sep 1999 11:38:33 +0100 John Hallam >> This is almost right. The time difference measured at the >>microphones is directly related to the difference in path length >>between >>source -> left microphone and source -> right microphone. In 2 >>dimensions, the set of points whose distances from two fixed points >>(foci) >>differ by a constant is a hyperbola; in 3 dimensions, the surface you > Of course this hyperbola (just like the ones drawn on marine >charts for LORAN navigation) go both in front and behind the person doing >the listening. I've always wondered how we can tell if a sound is in It is my understanding that a sound generated from a single point would propagate by spherical (not hyperbolic) waves, which can be approximated by plane waves at long distances from the source. Since the speed of sound is nominally 340 m/s (1087 ft/s), you will have to time the differential pulse detection quite accurately to get reasonable accuracy from microphone arrays that are not spaced very far apart. ================================================================ Robert A. LaBudde, PhD, PAS, Dpl. ACAFS e-mail: ral@lcfltd.com Least Cost Formulations, Ltd. URL: http://lcfltd.com/ 824 Timberlake Drive Tel: 757-467-0954 Virginia Beach, VA 23464-3239 Fax: 757-467-2947 "Vere scire est per causae scire" ================================================================