[acjohnson55]

To add an aside to my other comment, as a grad student in a spatial audio class, I led a project to create a new method of simulating physical reverb by using mics and speakers pointed at each other in an anechoic space, letting the mutual feedback create reverb. You could apply delay to "push back" the walls and apply filters matching the absorption characteristics of different materials. It was a fun project, which won my group Grad Project of the Year at my school's demo day. A couple commercial products and systems use similar concepts to achieve active acoustic control.

The paper is unfortunately behind a pay wall: http://www.aes.org/e-lib/browse.cfm?elib=16101