Bandwidth-limited passive suppression of cylindrical source radiation using metamaterial based acoustic superscatterers

This paper proposes a bandwidth-limited passive noise control system enabled by an acoustic superscatterer to suppress the far-field sound radiated from a vibrating cylindrical rod. Superscatterers are known to expand the rigid boundary of an object, thereby enhancing its scattering cross-section. The design of the acoustic superscatterer is based on the partially-resonant system in which a coating consisting of a double-negative metamaterial complementary to the host medium is provided around a rigid object. When a source lies within the enhanced boundary of the complementary medium, the interaction between this boundary and the wavefield originating from the source suppresses the total forward radiated sound in the far-field. An analytical framework for this phenomenon and numerical cross-verification examples are presented and discussed. The applicable bandwidth for superscattering and sound suppression thereof are also discussed with the help of integrated extinction theory, drawing conclusions vital for practical applications.