any idea on how max/msp could be used to find a persons location in a room using four microphones?
You could use a fiddle~ external on each of these microphones which will give you a number value for velocity. You could simply use an if statement to choose the one that was loudest, else if you were feeling adventurous you could come up with some matrix system where you could subdivide it between the values.
Might be easier to just use jitter and cyclops or something maybe? but depends waht you're trying to do- and with cyclops involved, budget!
You could also try introducing a continuous, high frequency sound into the room. Then watch for level changes from the microphone's input as the person casts a "shadow" moving around the room. High freq's are directional, so you might need to point a speaker at each microphone. I've used this technique in a studio setting before with one speaker and mic. I also recall seeing a Nord Modular patch that used the technique. You might try searching a Nord forum.