Demonstration of an air column resonance with a corrugated tube. Free

Standing waves, or resonances, will occur in an open‐ended tube when the air in the tube is excited at a particular frequency or its harmonics. The resonant frequencies are a function of the tube length. The first standing wave, fundamental mode or first harmonic, is set‐up with antinodes at each end of the tube, as the air is free to move at the ends, with one node in the middle of the tube. Each successive standing wave has an additional anti‐node and node, with the second harmonic containing three, antinodes and two nodes, the third containing four and three, respectively, and so on. This phenomenon of an air column resonance will be demonstrated using corrugated tubes. By spinning the tube overhead at a particular speed, the resonance frequencies will be excited. For slower speeds, lower frequencies will be heard, while the pitch will increase for faster speeds. Instrumental examples of open‐ended tubes include the flute and organ pipes.