Lance Lund, a professor at Anoka-Ramsey Community College, was asked to prepare a promotional science video for the college back in 1995 that was to air on a local cable access channel. All went well until he inhaled some sulfur hexafluoride (SF6). The video never aired, but many more of you from around the world will be able to enjoy this right here.
See how this balloon science experiment lets you speak in a high pitch squeal with air from a balloon, and with a low frequency voice from sulfur hexafluoride, which is very dense, five times more dense than air molecules, a lead balloon. Getting rid of the sulfur hexafluoride in you can be accomplished by simply standing on your head.