Design of acoustic coatings with symmetric and asymmetric resonant inclusions

An acoustic coating for underwater applications, designed using periodically distributed cavities and hard spherical particles embedded in a soft matrix, is herein modelled as monopolar and dipolar scatterers positioned along the centre of a sound hard duct. Modified equations of motion for the scatterers account for resonance phenomena as well as multiple scattering of waves by a lattice. Combinations of monopolar and dipolar scatterers in the direction of the incident sound field are considered. The acoustic performance of the various coating designs composed of symmetric and asymmetric resonant inclusions are compared. The influence of asymmetry in coating designs, arising from variation in scatterer size and material distribution, on effective material properties and Willing coupling are reported.