Determining the specific area of porous acoustic materials from water extraction data

The internal pore surface area per unit mass of solid (specific area) is an important parameter for the physical study of sound wave propagation in po rous media. It is shown that this parameter can be evaluated with a reasona ble accuracy from the integration of the water extraction curve (volume of water extracted versus applied pressure). This method is nonacoustic, model less and well adapted to acoustic materials. It is a complementary method t o the standard BET (Brunauer, Emmet, Teller) technique, generally used for powders in chemistry and the pharmaceutical industry. Experiments are made on loose glass beads of a few hundred microns diameter and results are comp ared to theoretical values. Results on heterogeneous materials used in civi l engineering and in noise control are also given. The parameters necessary for the description of modern acoustic materials are estimated from the sp ecific area measured by this method. (C) 1998 American Institute of Physics . [S0021-8979(98)04524-1].