Interaction of sound waves. I - Basic equations and plane waves. II - Plane wave and real beam

A theoretical study of the nonlinear interaction of sound waves in a lossless fluid is presented, with application to the parametric generation and reception of sound. The basic equations are shown to be valid to square-order terms in the acoustic variables. The effects of nonlinear on-source conditions are illustrated using plane wave models. In the second part, the basic equations are used to study the case of the interaction between a beam and an infinite plane wave. An integral solution is obtained in the quasi-linear approximation for the sum and difference frequency components, and a simple formula is obtained in the farfield region.