Wow -this may bug the heck out of your eyes but I think the thought that went into it is pretty cool. You say something that then is heard alone and then with everyone who went before you. The sound is also transmitted as an LED flash on a wall. Check it out.

“Voice Array” at MCA Sydney (2011) by Rafael Lozano-Hemmer from bitforms gallery on Vimeo.

Source: Lozano-Hemmer