Resonant elements for sonic crystal barriers.

Abstract

Multiple scattering in periodically spaced, vertically orientated cylinder arrays produces band gaps, the (Bragg) frequencies of which are determined by the lattice constants. For rigid cylinders these band gaps tend to have azimuthal angle dependency. Additional relatively angle-independent band gaps at frequencies below the first Bragg frequency can be obtained by use of resonant array elements. The results of laboratory experiments investigating the acoustical performance of four types of resonant elements are reported. These include slotted cylinders, thin-walled cylindrical elastic shells, concentric arrangements of slotted cylinders and elastic cylindrical shells, and multiply resonant elements consisting of hard-backed cavities between thin cantilevered plates. [Work supported by EPSRC (UK) Grant no. EP/E062806/1.]