Absorption of sound by porous layers with embedded periodic arrays of resonant inclusions

TLDR

The study aims to design a porous layer with broad‑band high acoustic absorption. The absorption is enhanced by low‑frequency resonances of slotted‑cylinder inclusions and energy trapping between the inclusions and a rigid backing, and a parametric study explores how inclusion geometry and arrangement affect the coefficient. Experiments show that embedding periodically arranged resonant inclusions markedly increases low‑frequency absorption compared to a plain porous layer.

Abstract

The aim of this work is to design a layer of porous material with a high value of the absorption coefficient in a wide range of frequencies. It is shown that low frequency performance can be significantly improved by embedding periodically arranged resonant inclusions (slotted cylinders) into the porous matrix. The dissipation of the acoustic energy in a porous material due to viscous and thermal losses inside the pores is enhanced by the low frequency resonances of the inclusions and energy trapping between the inclusion and the rigid backing. A parametric study is performed in order to determine the influence of the geometry and the arrangement of the inclusions embedded in a porous layer on the absorption coefficient. The experiments confirm that low frequency absorption coefficient of a composite material is significantly higher than that of the porous layer without the inclusions.