Singing corrugated pipes

Abstract

A corrugated tube open at both ends, with air flowing through the tube, sings notes which depend on the flow velocity and the length of the tube. The notes it sings are the natural harmonics of the tube. A given note will sing when the flow velocity is such that the frequency at which the air bumps into the corrugations is close to the frequency of the note, provided that the flow velocity is sufficiently high to induce turbulent flow. Study of this phenomenon [F. Crawford, Am. J. Phys. 42, 278 (1974)] has led me to invent a new family of wind instruments I call Corrugahorns. The simplest of these is the Corrugahorn Bugle. It plays harmonics third to about tenth, plus additional notes obtained by tricks (finger flatting, whistle flatting, palm sharpening) that give it almost a complete chromatic scale. The most sophisticated is the Slide Corrugahorn, with a slide (like a trombone) that gives it a chromatic scale over its range. I will demonstrate various singing corrugated pipes, including corrugahorns and another instrument I call the Water Pipe.