H3-13
Demonstrate standing sound waves in air excited by convection currents.
A switch is held closed, heating a nichrome wire coil in a vertical four-inch diameter galvanized steel downspout tube, leading to a very loud roar at about 65 Hz, the fundamental frequency of an eight-foot air tube. This is the classic Rijke tube demonstration with an electrical heater replacing a gas burner and screen as the source of the convection currents.

Consider combing this with H3-12, and invite students to make predictions about the differences in pitch and volume.

h3-13coilh3-13drawing