Enhancing sound attenuation in multiscale porous materials via diffusion processes, by Rodolfo Venegas (ENTPE)Jan. 24, 2017
DENORMS Action’s Workshop “Modelling of high performance acoustic structures Porous media, metamaterials and sonic crystals”, Rome, 24-25th January 2017
Session on New trends in traditional noise treatments – porous materials and microperforated plates
Speaker: Rodolfo Venegas (ENTPE)
We investigate different types of diffusion processes in multiscale porous materials with well separated scales. These processes appear as a consequence of inter-scale interactions and allow enhancing the materials low-frequency sound attenuation. We successively use the two-scale asymptotic expansion method of homogenisation for periodic media to establish the macroscopic description of sound propagation through three different classes of materials. The first class corresponds to double porosity sorptive materials where inter-scale mass diffusion and sorption processes occur. These effects are manifested macroscopically through a decrease in speed of sound in the material and an increase of low-frequency sound attenuation. The second class corresponds to triple porosity sorptive materials where inter-scale mass diffusion and pressure diffusion, both being influenced by sorption, determine the decrease in sound speed and enhanced low-frequency sound attenuation in the materials. The third class corresponds to heterogeneous porous materials where multiple pressure diffusion processes are induced by introducing mesoscopic geometrical alterations and/or material heterogeneities. The resulting multiscale porous composites show enhanced low-frequency sound attenuation in comparison to that achieved by its constituents separately. The theories are validated by either conducting experiments or via numerical simulations showing in both cases good agreement.