Giant nonlinearities in structurally inhomogeneous media and the fundamentals of nonlinear acoustic diagnostic techniques

The mechanisms responsible for anomalously strong acoustic nonlinearities in multiphase, defected, and structurally inhomogeneous media are summarized, and nonlinear diagnostics — a fast-growing applied area of recent years — is reviewed in terms of its methods and applications. This paper is an expanded version of the introductory talk at the September 18, 2005 session of the RAS Physical Sciences Division. An abridge version of other talks presented in the session is also given in this issue of Physics–Uspekhi.