ASA 127th Meeting M.I.T. 1994 June 6-10

2pPA11. Reflection and transmission of a finite amplitude focused sound beam at a curved interface between two media.

Inder Raj S. Makin

Dept. of Eng., Swarthmore College, Swarthmore, PA 19081-1397

Biomed. Eng. Program, Univ. of Texas at Austin, Austin, TX 78712

The talk will present further work on the interaction of a finite amplitude, focused sound beam with a curved interface separating two fluidlike media. An earlier presentation [Makin and Hamilton, J. Acoust. Soc. Am. 89, 1928 (1991)], had discussed the second harmonic generation in a focused Gaussian beam that is reflected from a slightly curved surface. As earlier, arbitrary absorption and complex surface impedance can be taken into account in the current model. The quasilinear analysis is now extended to a fully nonlinear numerical evaluation of the KZK equation using a finite difference method. An existing model for the free-field propagation of a high intensity focused sound beam [Tj(slashed oh)tta et al., J. Acoust. Soc. Am. 89, 1017--1027 (1991)], has been modified to evaluate the fields reflected and transmitted from a curved interface between two media. Propagation curves, beam patterns, phase plots, and time waveforms for various parametric combinations of source conditions and media pairs are presented, highlighting the effect of the interface curvature on the reflected and transmitted beams. Significance of the work in terms of biomedical applications is discussed. [Work supported by NSF and the David and Lucile Packard Foundation.]