ABSTRACT
In this chapter, the authors discuss weakly nonlinear hyperbolic waves. They present a nonlinear extension of the high-frequency expansion method and discuss combined effects of dispersion, dissipation and nonlinearity. In a nonlinear problem, the authors must also consider the order of magnitude of the perturbation amplitude, and therefore there is one parameter more than in the linear case. In the nonlinear high-frequency expansion method, the wave propagates along the bicharac-teristics of the unperturbed state and the nonlinearity, shows itself in a modified transport equation for the amplitude. The authors use the general theory to analyze the propagation of sound waves through a stratified athmosphere.
