High broadband absorption of acoustic waves by elastic-framed metaporous layer

The acoustic behaviour of a metaporous materials constituted of resonant elastic shells embedded in a poro-elastic matrix is reported. The acoustic plane wave reflection from such an elastic-framed metaporous layer glued against rigid backing is studied. The analysis is performed by applying the multiple scattering theory in a dissipative Biot continuum while accounting for the fields scattered by the inclusion at the layer plane boundaries. It is shown that high broadband absorption of sound is achieved through the coupling of resonances of both the array and the shells with visco-thermal and elastic losses in the poro-elastic matrix. Moreover, the excitation of flexural resonances of the shells enable high-quality absorption of sound in the deep subwavelength regime. The semi-analytical approach of these multi-physical phenomena underlines the complex interactions between the scatterers and the poroelastic matrix, and allows the efficient computation of the fields.