Specific acoustic impedance measurement by a protruding tube method

Abstract

A method is described for measuring the acoustic parameters (structure constant and damping constant) of porous absorbing materials using an open-ended tube which is inserted into the test material. The specific acoustic impedance at the face of the sample in the tube is measured and the required acoustic parameters are determined from these measurements. The results obtained from measurement on two flexible foams agree with previously determined values. The technique offers increased precision over the open flanged tube method but its range of application is more restricted.