To demonstrate dramatically standing waves in a tube.
Flame tube with audio oscillator, microphone and amplifier, and audiocassette player with audiocassette,◙permanently assembled on rolling stand as photographed.
A loudspeaker in one end of a four-inch diameter galvanized iron tube creates standing waves in propane gas in the tube. The gas emerges out of a series of small holes in the top of the tube, forming a long line of flames when lit. Any sound resonant with the length of the tube can create standing waves in the gas which are readily visible as a pattern in the height of the flames. Both rhythm and frequency response can be seen nicely in music. An oscillator or a voice introduced using a microphone and amplifier provided with the demonstration can be used as simple sources for the loudspeaker.
Instructions for the Use of A 20 lb LP-Gas Cylinder, Instruction Manual for Single and Second Stage LP-Gas Regulaors,Fisher Controls Co. ◙R. J. Stephenson and G. K. Schoepfle, A Study of Manometric Flames, AJP 14, 294-299, (1946). ◙Jerry L. Underfer, Misconceptions About Resonance in Vibrating Air Columns, TPT 4, 81-83, (1966). ◙Roy Coleman, The Flaming Air Track, TPT 13, 556-557, (1975). ◙Mario Iona, Pressure in Standing Waves, TPT 14, 325, (1976). ◙Thomas D. Rossing, Average Pressure in Standing Waves, TPT 15, 260, (1977). ◙Robert P. Bauman and Dennis Moor, More on Dancing Flames, TPT 14, 38