We develop an analytic, unified, and systematic methodology based on scattering theory, for determining the dynamic (frequency-dependent) effective properties of micro-inhomogeneous (visco) elastic media, such as effective elastic moduli, wave speeds, and wave attenuations. The small inhomogeneities are modeled deterministically as fluid-filled spherical cavities, and the Ament–Toksöz method for obtaining static effective properties is extended to the dynamic (resonant) case by retaining those higher-order terms in a long wavelength expansion which give rise to the ultrasonic resonances of the microinhomogeneities. Rescattering from the inhomogeneities has been neglected, thus restricting the applicability of our results to the case of moderate inhomogeneity concentrations. The results of the present analysis are affected by the presence of shear waves in the solid matrix, and they contain all the findings of our previous dynamic resonance theory of gas bubbles in liquids, as well as nearly all the static results available in the earlier literature which do not take rescattering effects into account, as particular cases. We graphically display many numerical results for fluid-filled cavities in rubber matrices.