Problems in nonlinear acoustics: Pulsed finite amplitude sound beams, nonlinear propagation of sound in layered media, time domain solutions for focused sound beams, focusing of sound with an ellipsoidal mirror, and modeling finite amplitude propagation in waveguides

Abstract : Five projects are discussed in this annual summary report, all of which involve basic research in physical acoustics, mainly nonlinear acoustics. (1) Pulsed Finite Amplitude Sound Beams are investigated numerically with a time domain computer algorithm, and experiments are underway to study nonlinear self- demodulation. (2) Nonlinear Propagation of Sound in Layered Media involves studies of shallow water above a penetrable bottom (both theory and experiment) and the SOFAR channel (only theory). (3) Time Domain Solutions for Axial Pressures in Focused Sound Beams is a theoretical comparison of three different models. (4) Focusing of Sound with an Ellipsoidal Mirror is a theoretical study of the reflected field, typically short pulses, along the axis of the mirror. (5) Modeling Finite Amplitude, Propagation in Waveguides with a Nonlinear Parabolic Wave Equation is a new project that involves both theory and experiment.