Broadband attenuation of spherical acoustic waves using radial sonic crystals with diverging geometries

In this study, we propose various designs of radial sonic crystals (RSCs) incorporating radially distributed resonators to attenuate sound waves propagating outward from a central source. The RSC configurations are shown to effectively suppress sound waves with spherical wavefronts, particularly in the low-to-mid-frequency range where wavefronts remain curved before transitioning to planar profiles. Among the explored designs, RSC-I, which features a diverging radial geometry and circumferential periodicity, demonstrates superior attenuation compared to a uniform RSC (URSC) with consistent resonator spacing. Furthermore, RSC-II structures, characterized by periodicity in both radial and circumferential directions, outperform RSC-I in broadband attenuation. Three RSC-II variants, each employing different resonator slot configurations, are evaluated using finite element (FE) simulations to assess their frequency-dependent performance. A parametric investigation of radial and circumferential lattice constants in RSC-II further reveals their influence on bandgap formation and insertion loss (IL). Unlike conventional sonic crystals (SCs) designed for far-field attenuation, the proposed RSCs can be utilized for near-field noise control, making them well-suited for applications that require source-proximal acoustic mitigation.