Resonance reflection of acoustic waves by a perforated bilaminar rubber coating model

Abstract

We construct the prediction of the resonance scattering theory (RST) for the reflection of sound waves by a bilaminar rubber configuration separating two dissimilar semi-infinite acoustic media. The layers are further assumed to contain distributions of spherical air-filled perforations, of various concentrations in each layer, whose behavior is governed by a simple, static, "effective parameter" model. We compare the direct scattering prediction of the RST to that of the exact solution in order to show the usefulness of the RST to yield clear physical interpretations of complex phenomena. The casting of the direct scattering solution in "RST-form" also provides a systematic method to solve the inverse scattering problem for the composition of the bilaminar rubber configuration. The "response surface" and response curves of the returned echoes are shown to contain certain modulation effects, described in the text, that actually characterize the material composition of each of the layers making up the coating model. The process disentangles which resonance feature present in the reflection coefficient is caused by which one of the interacting layers. In particular, we can separate and identify the impedances and the respective thickness-to-speed ratios (transit times) of each of the layers, and if additionally, either the thicknesses or the speeds are known, then, the process determines the other one and also the layer densities all from the resonances in the remotely sensed acoustic reflections.

Acoustic performance prediction of anechoic layer using identified viscoelastic parameters

“…There have been many studies to analyze and predict the acoustic performance of anechoic layers. Jackins and Gaunaurd (1983) used resonance scattering theory to predict the reflection characteristics of bilaminar coatings, where each layer contained spherical cavities in small concentration can be described using an effective medium. Furthermore, Strifors and Gaunaurd (1990) conducted various studies on the reflection of a plane wave impinging on such a bilaminar structure.…”

Multi-focus design of underwater noise control linings based on finite element analysis

“…Fiorito et al [5] studied interaction of sound waves with these viscoelastic linings and gave analytical expressions for transmission and reflection of sound waves through such linings without any air cavities. More complex configurations with cavities in the coating have been analyzed using analytical methods [6][7][8]. Jackins and Gaunaurd [6] used their resonance scattering theory to 0003-682X/$ -see front matter Ó 2007 Elsevier Ltd. All study the effect of bi-laminar coatings where each layer was assumed to contain uniform clouds of air bubbles of known, different, and small concentrations.…”

“…More complex configurations with cavities in the coating have been analyzed using analytical methods [6][7][8]. Jackins and Gaunaurd [6] used their resonance scattering theory to 0003-682X/$ -see front matter Ó 2007 Elsevier Ltd. All study the effect of bi-laminar coatings where each layer was assumed to contain uniform clouds of air bubbles of known, different, and small concentrations. Specifically, they also analyzed the case of sound reflection by two pure rubber layers ideally bonded to each other.…”

Simplified model for predicting acoustic performance of an underwater sound absorption coating

“…Gaunaurd (1977, 1985) and Lane (1981) presented a one-dimensional analysis method for a viscoelastic medium which contains short cylindrical cavities, and they provided a physical explanation based on different modes of resonances which are correlated with different physical dimensions of cavities. Jackins and Gaunaurd (1983) used the resonance scattering theory to predict the reflection characteristics of bilaminar coatings, where each layer containing spherical cavities of small concentration can be described by an effective medium. As a related problem, studies on the reflection of a plane wave impinging upon such a bilaminar structure have been finished by Strifors and Gaunaurd (1990).…”