There are a couple ways I could imagine doing this. One way would involve a bit of audio trickery. What I'm thinking is running the left and right speakers from each computer *seperately* to the other rooms. You could then create stereo sound files that play white noise only in the left or right sound channel (easy to do--let me know if you need help with that). You then create simple skip patterns in MediaLab (or DirectRT) that allow the subject to select which sound file to play.. voila--a blast directed to one room or the other.