Physical Mechanisms for Biological Effects of Sound

Understanding and control of sonic action on biological cells requires continued development of acoustical theory and of experimental procedures. Available nonlinear theory is helpful in explaining intracellular stresses, displacement, and circulations produced by sound; but the analysis must be generalized to deal with gellike media. When cellular envelopes are ruptured by sonic irradiation of cell suspensions, the destruction is usually ascribed to “cavitation,” whose role is not well understood. In recent experiments with red cells, bubble activity is controlled by degassing the suspension and then deliberately providing air in one or more “pockets” of suitable size. On studying effects of various parameters, it is found as in earlier work [Hughes and Nyborg (1960)] that cellular changes result at much smaller amplitudes than are required for such phenomena as sonoluminescence. These changes probably result from small‐scale motions of and near the bubbles. Details of bubble‐associated motions are being studied with low‐frequency large‐scale arrangements. [Work supported in part by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]