Propagation in Inhomogeneous Media (Ray Theory)

This chapter describes how ray theory may be extended to allow for nonlinear waveform distortion in inhomogeneous media. Considered first are stationary media, and examples related mainly to underwater sound are presented. The theory is generalized to account for moving media, for which a distinction between ray and wavenormal directions becomes necessary. Examples with moving media are presented in relation to aeroacoustics and sonic boom propagation. The theory is restricted to weakly nonlinear acoustic waves in a slowly varying medium that is not strongly dispersive. The chapter concludes with a discussion of relevant acoustical properties of water and seawater.