Hoot tubes, also known as singing tubes, are vertical tubes that produce sound when heated at one end. A Bunsen burner heats a screen or gauze at the bottom of a large open vertical tube. The heated air inside the tube creates a convection current, causing the air to oscillate and produce a sound. This demonstration shows the principles of resonance and the effect of temperature on sound production, as well as the characteristics of standing waves in a column of air.