Measurement and modeling of the open end correction for driven pipes.

Abstract

The end correction that accounts for the inertial impedance at the open end of a pipe is a widely used refinement to lumped-element models, and many variations have been investigated. This study measures the end correction for 1 m closed-open pipes of varying diameters, exposed to a single-frequency external sound field created by a subwoofer in an anechoic facility. The frequency response of each pipe was measured as the ratio of the pressure at the closed end of the pipe to a reference pressure at the open end. Using an expression for the predicted mode frequencies based on the assumption that the driving pressure is uniform across the open end, the driven end correction was derived from the measured frequency response. The interaction of the pipe and the external sound field can be visualized in a finite element model, with alternative estimates of the driven end correction. Preliminary results indicate that the driven end correction can be as large as the diameter, more than three times the expected value for a passive open end.