Acoustical behavior of a submerged steel plate coated with an elastomer layer that contains perforations

Abstract

The reflection and transmission characteristics of an infinite steel plate submerged in water are analyzed for a normally incident plane acoustic wave. The plate is coated on one side by a layer of styrene-butadiene rubber (SBR) perforated by a doubly periodic array of rectangular holes. A second, thin, homogeneous SBR layer covers the perforated layer so as to exclude water from the holes. Numerical analyses are presented that compare two different models describing the perforated layer—the “effective-modulus” model and an alternative model derived using an approximate elasticity-theory analysis. In the effective-modulus model, only the volume concentration of the perforations in the SBR affects the elastic properties of the layer. However, in the alternative model, the layer elastic properties are affected by the size, shape, and pattern of the perforations, in addition to their concentration. The effects of perforation size, shape, and pattern are illustrated by comparing computed results for different perforation schemes having the same volume concentration of perforations.