NONLINEAR PROPAGATION IN AN OCEAN ACOUSTIC WAVE-GUIDE

The nonlinear progressive wave equation (NPE) is used to investigate propagation of acoustic pulses in a shallow ocean waveguide. The nonlinearity is shown to affect transmission and reflection at a fluid fluid interface. It is shown that one effect of the nonlinearity is to reduce the critical angle for total internal reflection from that of the linear case. When loss versus range for a simple isovelocity waveguide is compared with linear normal mode and parabolic equation calculations, the nonlinear result shows increased transmission loss as long as the wave amplitude is significant (an expected result of shock processes), and increased bottom penetration. Nonlinear aging of the waveform alters the excitation of linear modes in the farfield. © 1990, Acoustical Society of America. All rights reserved.