Acoustic Interaction Effects in Arrays of Small Spheres

Abstract

Multiple acoustic scattering in line and plane arrays of spheres can sometimes reduce the acoustic pressure on the sphere surfaces to well below the free-field value, especially for gas-filled spheres. However, at spacings near half a wavelength, there can be an enhancement. The resonance phenomenon is much sharper for a single spherical bubble than for a cylindrical bubble, a cylindrical vortex, a line of spheres, or a plane array of spheres. For finite arrays, the end or edge effects can be quantitatively described by additional geometrically spreading waves, but only when the above pressure reductions are small and only close to the edge. With high scattering, a modified edge wave must be used. [Hudson Laboratories of Columbia University Informal Documentation No. 79. Work supported by the U. S. Office of Naval Research.]