REFLECTIONS FROM STEEL PLATES WITH DOUBLY PERIODIC ANECHOIC COATINGS

摘要

A thin rubber coating with cavities in a doubly periodic lattice can redistribute sound energy, normally incident on a steel plate, in the lateral direction. At high frequencies, propagating reflected beams appear in a discrete set of nonnormal directions in the surrounding water. The phenomenon -is illustrated by pulse measurements in a water tank. The results are modeled by adapting modern computation techniques for electron scattering and band gaps in connection with photonic and phononic crystals. At lower frequencies, with only one propagating reflected beam in the water, differential evolution and winding-number integral algorithms are applied to design coatings with low reflectance. A stochastic resampling algorithm is adapted for accurate characterization of the parts of parameter space with favorable properties.