SCATTERING OF SOUND BY SOUND FROM 2 GAUSSIAN BEAMS

The scattering of sound by sound from Gaussian beams that intersect at small angles is investigated theoretically with a quasilinear solution of the Khokhlov-Zabolotskaya nonlinear parabolic wave equation. The closed form solution, which is valid throughout the entire paraxial field, is a generalization of a result obtained previously for parametric receiving arrays [Hamilton et al., J. Acoust. Soc. Am. 82, 311–318 (1987)]. Significant levels of scattered sum and difference frequency sound are shown to exist outside the nonlinear interaction region. An asymptotic formula reveals that sound is scattered in the approximate directions of k1 + k2where kj is the wave vector associated with the axis of jth primary beam. Computed propagation curves and beam patterns demonstrate the dependence of the scattered radiation on interaction angle, source separation, ratio of the primary frequencies, and source radii. Comparisons are made with the farfield results presented by Berntsen et al. [J. Acoust. Soc. Am. 86, 1968–1983 (1989)], which are valid for arbitrary interaction angles, source separations, and amplitude distributions. © 1990, Acoustical Society of America. All rights reserved.