This lab doubles as a sound and heat lab. A stainless screen is inserted into one end of a piece of metal pipe that is 18" long. The screen is heated with a propane torch. When the screen becomes red hot, the flame is removed and warm air starts to rise and vibrate inside the tube. As the air vibrates it produces a low-pitched humming sound. If you tip the tube sideways the sound stops momentarily until you right the tube. Creates the illusion that you are pouring sound.