Acoustic superscatterers for passive suppression of cylindrical source radiation in the forward direction

TL;DR

This paper introduces acoustic superscatterers that use resonant coatings or metamaterials to suppress forward radiation from cylindrical sources, with analytical and numerical validation for potential practical uses.

Contribution

The study provides an analytical framework for passive suppression of forward acoustic radiation using superscatterers with cylindrical sources, including derivation of extinction cross section and effects of source geometry.

Findings

Suppression of forward radiated sound achieved by superscatterers.

Analytical expressions for extinction cross section derived.

Numerical verification confirms the effectiveness of the proposed method.

Abstract

Superscatterers are known to expand the rigid boundary of an object thereby enhancing the scattering cross section of the object. The design philosophy of the acoustic superscatterers is based on partially-resonant systems in which a coating material or double-negative metamaterial complementary to the host medium is provided on top of the rigid object. When the source lies within the enhanced boundary of the complementary media, the interaction between the radiated wavefront and the enhanced virtual boundary gets stronger and results in suppression of the total forward radiated sound at far-field. An analytical framework is shown in this paper on suppression of the total acoustic pressure at far field in the forward direction when a cylindrical source, both monopole and dipole, lies within the virtual rigid boundary of the superscatterer. Total extinction cross section of the scatterer as a function of the distance between the source and scatterer is derived to substantiate the earlier results. Additionally, the effect of the area of cross-section of the cylindrical source on the total forward radiated sound pressure at far-field is discussed. Finally, the effectiveness of the analytical results is verified numerically and the prospects for practical applications are discussed.