The vortex motion causing edge tones

Abstract

A detailed investigation has been made of the tones produced when a jet of air strikes an edge, with velocities extending from the lowest possible to those in the neighbourhood of the Reynolds critical velocity in the orifice. Four different stages of stable vortex-formation occurred and the whole phenomenon was found to lie within the sound-sensitive range of the jet. Throughout this range the dependence of the frequency n on the distance h of the edge and the mean velocity U can be closely represented for a 1-mm. slit-width and a wedge of angle 20° by the formula n=0.466 j (U-40) (1/h-0.07), where j=1, 2.3, 3.8 and 5.4 for the four stages respectively.