Applications of the Dual Porosity Theory to Irregularly Shaped Porous Materials

Non planar acoustic materials may be used in building and environmental acoustics to achieve a significant absorption at low frequencies. Examples of these materials are anechoic wedges or advanced design noise barriers. The shape of these materials is mainly based on empirical knowledge because a fine numerical modeling (e. g. FEM, BEM) requires large computational costs. Therefore, the optimisation of the general form and of the material used to realise these absorbing systems is limited. The purpose of this paper is to propose an original alternative to these limitations. The work basis relies on the theory for the acoustics of multi-scale porous materials, and in particular on double porosity materials, which has been initiated by Olny and Boutin (J. Acoust. Soc. Am. 2003, 114(1)). It is shown in this paper that this theory could be successfully applied to the modeling of non planar sound absorbing materials. Examples are given for multi-layer systems involving perforated panels, material samples having an irregular surface and anechoic wedges. The discussion is based on comparisons between analytical simulations and measurements.