The Beat... Think about the last time you heard a test of the Emergency Broadcast System. A couple of things to note: first, they say "For the next 60 seconds..." but they play the tone for a lot less than 60 seconds. And second, the tone that they play is very annoying. How do you make such an annoying tone? The answer: beats! Auditory Illusion You are all familiar with the idea of an optical illusion: something that tricks your eyes. The animation below will run an auditory illusion: something that tricks your ears. Airplane Noise Simulator A flight is represented by the intersection of its noise bubbles with the surface of the earth.