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

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 ah-flow technique. The r esults of these tests are compared with the corresponding values obtained b y an acoustic technique. The latter relies on the assumption that at very l ow frequencies the real part of the normal-incidence flow impedance of a th in porous layer is very close to its steady-state ah-how resistance. The me asurements results confirmed the above mentioned assumption to a certain de gree. To the knowledge of the authors, no previous comparison of steady-sta te air-flow versus oscillating air-flow measurement of the resistivity of t he considered granulates has been published yet. (C) 1999 Acoustical Societ y of America. [S0001-4966(99)00909-1].