What if, instead of using time of arrival to determine where a sound comes from, you use directional microphones. Or you use some sort of muffling cone to reduce the sound energy that reaches the mike from behind. Then you could measure sound intensity from all of the mikes and compare loudness to get a direction. Its not as sophisticated as the timing approach, but it might be easier to implement given the simple situation you describe with a single loud noise. Maybe you need decibel meters and not microphones. Sounds cool. Good luck.