Acoustic performance of a lattice of closely spaced hard inclusions in a soft medium

Abstract

Marine vessels are covered with an acoustic coating for underwater noise control. Acoustic coatings comprise a soft rubber-like medium embedded with periodic inclusions. Common inclusion types include cavities or hard metallic scatterers. A coating design comprising hard inclusions can exhibit consistent performance under hydrostatic pressure. In this work, analytical and numerical models are developed to predict the acoustic performance of a lattice of closely spaced hard inclusions in a soft medium. The analytical model is based on homogenization which allows the modelling of a complex medium as a homogenous medium with effective material and geometric properties. The effective properties account for the resonance of the inclusions and multiple scattering of waves between them. The numerical model is based on the finite element method and is developed using COMSOL Multiphysics. Results show that the dipole resonance of hard inclusions in a soft medium leads to high sound absorption. Reducing the spacing between the inclusions enhances multiple scattering of waves, resulting in higher sound absorption.