PARTICLE-LOADED COMPOSITES FOR ACOUSTIC ANECHOIC COATINGS

We consider here composite coating layers to be used as ''acoustic abs orbers'' which are able to attenuate broad-banded acoustic signals and minimize reflection. In order to effectively attenuate the acoustic w ave, a loaded composite coating layer is designed with a binder materi al and loading configuration combination that allows both impedance ma tching between the fluid and material front face as well as extinction of the signal due to scattering and absorption effects. We discuss in detail the scattering of elastic waves from elastic spheres and emplo y an exact Mie-scattering solution to this problem. We then develop a new formal hierarchy for the multiple scattering of elastic waves, whi ch is used to calculate the bulk wave properties of the composite coat ing. Using these results we show the reflection coefficient for a comp osite coating layer as a function of scatterer size and coating thickn ess for a variety of cases.