Steady-state air-flow and acoustic measurement of the resistivity of loose granular materials

Abstract

In the course of a study for characterizing the acoustic properties of some loose granulates made of limestone chips, the authors have measured their resistivity in a very simple way by a steady-state air-flow technique. The results of these tests are compared with the corresponding values obtained by an acoustic technique. The latter relies on the assumption that at very low frequencies the real part of the normal-incidence flow impedance of a thin porous layer is very close to its steady-state air-flow resistance. The measurements results confirmed the above mentioned assumption to a certain degree. To the knowledge of the authors, no previous comparison of steady-state air-flow versus oscillating air-flow measurement of the resistivity of the considered granulates has been published yet.