Wave scattering by small impedance particles in a medium

The theory of acoustic wave scattering by many small bodies is developed for bodies with impedance boundary condition. It is shown that if one embeds many small particles in a bounded domain, filled with a known material, then one can create a new material with the properties very different from the properties of the original material. Moreover, these very different properties occur although the total volume of the embedded small particles is negligible compared with the volume of the original material.