Sound absorption by acoustic microlattice with optimized pore configuration.

The great progress in material science and nano-micro fabrication enables the applications of metamaterials with well-defined and well-organized microstructures for noise reduction. However, what intrinsic morphology of the metamaterial would result in optimum sound absorbing efficiency remains uncertain. This work presents a microlattice metamaterial, comprising well-defined and organized material morphology in terms of pore size and porosity, for generating optimum sound dissipation. A compact governing equation is established and verified experimentally to show that the optimum sound absorption can only be reached when the pore size equals twice the thickness of a viscous boundary layer.