Flame Tube 2012
I love teaching high school physics, and one of my favorite demonstrations every year is the Ruben's Tube I've made to show my kids a visual representation of sound waves.
Basically, it's a long metal tube with holes drilled in the top. I've got gas (propane works well) running through the line, which ignites when lit. I put the subwoofer of my speakers up in front of one end of the tube (which is blocked off with a soft membrane) to send vibrations into the tube. The vibrations of the low notes change the pressure in the tube, which changes the height of the flame.Flame Tube 2012