Wave-obstacle interaction in a lossy medium: energy perturbations and negative extinction

The concept of a generalized extinction cross-section introduced in a previous paper is given in detail and exemplified by the problem of scattering by an elastic cylinder embedded in a viscoelastic matrix. It is shown that under certain conditions the presence of inclusion may have a supporting effect on wave propagation (negative extinction). The derived low-frequency expansions indicate that the Rayleigh law may not hold in the case of a lossy medium. Numerical results as well as discussions concerning separation between scattering and intrinsic viscoelastic losses are also given.