The K-coupler, a new acoustical-impedance transformer

The validity of a new approach to the problem of matching the acoustical impedance of a piston to the acoustical impedance of the medium into which it radiates power is examined. The device, called a K-coupler, consists in part of a duct or pipe which has an exponentially increasing opening cut in one side. It is shown that the behavior of the K-coupler may be approximately described by the use of equations similar to those that describe the behavior of an exponential horn. Experimental data that show input impedance as a function of frequency are presented.