Load this video, but pause put it on mute:
http://www.youtube.com/watch?v=mGMzGxeO1wQ

Then load this video and don't mute it.
http://www.youtube.com/watch?v=shDNaFhPiJY

Hit play on both, watching the one on mute with the sound playing on the other.

Maryn, promising it's safe for work and under two minutes