I started to give a physics explanation for why this looks the way that it does, but the page has a great explanation.

Unfortunately, it doesn't really do much to describe naturally and even unnaturally occurring vibration and/or sound. What it can show is that phase CAN matter (as the interesting visual patterns result from all of the various slightly varying phase of the individual pendulums).

It does look cool, but can actually be more confusing for explaining sound to someone than simpler demonstrations of more naturally occurring wave combinations.

-Scott

-Scott