The Physikanten hold two similar glass tubes above two Bunsen burners. The tubes are equipped with a wire mesh about 10cm from the bottom. When the tube is removed from the fire a loud tone is clearly audible. The Physikanten demonstrate some very cool effects using this tone.
How does it work?
The wire mesh at the bottom of the tube heats up the surrounding air. The air expands and produces a small pressure wave. The wave is reflected at the top and travels back down the tube. The hot air around the mesh is blown away by the wave, allowing the air around it to expand once more and produce the next wave. This process repeats and causes the tube to resonate and vibrate, generating a loud tone.
