Coil, Glowing and Humming
The Rijke Tube consists of only a heat source (the glowing wire coil) in a vertical tube; once enough heat power is supplied, the interplay of heat exchange and induced velocity fluctuations yields a loud, steady hum -- a manifestation of what is known as thermoacoustic instability phenomena.
Our Rijke Tube is constructed of a glass tube of about 4 feet and a NiCr (Nickel Chromium) wire coil mounted in the lower section of the tube. Both ends of the tube need to be open. Typically, by the time the temperature is high enough to yield sufficient heat exchange between wire and surrounding air, the coil is glowing red, which is what we see in the photograph. The camera is placed on top of, and facing down into the tube; the (Pyrex) glass yields the circular reflections.