Dynamics of Acoustic Resonance Scattering from Spherical Targets.
Interim technical rept. 1 Nov 77-31 Jan 79,
CATHOLIC UNIV OF AMERICA WASHINGTON D C DEPT OF PHYSICS
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A resonance theory of acoustic scattering from penetrable bodies has recently been developed which describes the features of the scattering amplitude in terms of a background amplitude like that of an impenetrable scatter, with superimposed resonances at the eigenfrequencies of the body. In the present study carried out for the example of a spherical gas bubble in a fluid which in spite of its simplicity contains all the essential features of the scattering process, the existence of these resonances is explained by the phase-matching of surface waves on the scatter whose phase and group velocities are obtained here. In addition, we study the dynamics of the interior motions inside the body during the scattering process, which are shown to undergo resonances in the radial and angular directions except for the radial motions of the surface, resulting in the fact that the modal surface deformations do not exhibit any particular resonance effects at the eigenfrequencies of the body.