ASA 124th Meeting New Orleans 1992 October

3aPA13. A theoretical investigation of a highly intense sound beam from a plane circular transducer.

Aina M. Berg

Jacqueline Naze Tj(slashed oh)tta

Sigve Tj(slashed oh)tta

Dept. of Math. and Dept. of Phys., Univ. of Bergen, Allegt. 53, 5007 Bergen, Norway

Sylvain Nachef

Technomed Internatl. SA, Bron, France

The experimental investigation reported by Nachef et al. (see preceding abstract) represents a good opportunity to assert the validity of the transformed beam equation and its numerical implementation [Naze Tj(slashed oh)tta et al., J. Acoust. Soc. Am. 88, 2859--2870 (1990)], and their usefulness to simulate highly intense sound beams. Comparison between theoretical and experimental results shows that in spite of the fact that it does not account for higher-order nonlinear effects, the model reveals a remarkable ability to accurately simulate the fine structure of the sound field, at any range and level of excitation under consideration. The present theoretical investigation confirms the nonlinearly induced shift in the near-field structure of the beam (defocusing) experimentally discovered by Nachef et al. [Work supported by The Norwegian Research Council for Science and Humanities (NAVF), and Fondation Scientifique de Lyon et du Sud-Est, France.]