Passive End Correction of Pipes and Resonators

When a pipe is sounded by blowing across the mouth, the sounding frequency can be varied by adjustment of the stream speed so as to be either above or below the natural pipe frequency, an effect observed but not explained by Rayleigh [Phil. Mag. Set. 5, 13, 340–343 (1882)]. As a pipe is “blown up” to pitch, the pipe‐mouth end correction may be considered to have an active component, due to the presence of the jet, whose reactive part varies from positive to negative as jet‐feedback control shifts from edge to pipe. The positive reactance derives from the edge‐induced “dipole” field while the negative component can be determined from the pipe‐jet transfer function. Experimental data are presented. [Work supported by the Office of Naval Research.]