An experimental study of the oscillations in a flue organ pipe

Abstract

Stationary oscillations of a simple flux‐type organ pipe have been studied. Internal acoustical pressure measurements in combination with modification of pipe geometry indicate that the sound source at the labium is a dipole. This observation is explained by Coltman's analysis [J. Acoust. Soc. Am. 60, 725–733 (1976)]. The jet oscillation observed by flow visualization is compared with theories by Cremer and Ising [Acustica 19, 144–153 (1967/68)] and Fletcher [Ann. Rev. Fluid Mech. 11, 123–146 (1979)]. Both theories lack a firm mathematical background; there are, however, no better theories available at the present time. Vortex shedding at the labium is observed in the course of the starting transient and for high‐blowing pressures during stationary oscillations. Theory indicates that these vortices can induce a significant nonlinear damping for stationary oscillations.