Scattering and Radiation of High Frequency Sound in Water by Elastic Objects,Particle Suspensions, and Curved Surfaces

摘要

The research reported is principally in the areas: (A) Scattering of high-frequency sound or pressure impulses by elastic objects in water--Experiments and theory are examined for scattering of pressure impulses and high-frequency sound by elastic objects in water. Improved capability for measuring the impulse response is discussed and examples given include: (1) the bipolar specular feature that reveals the mass-per-area of the shell; (2) the beating of low frequency flexural modes of a shell; and (3) the impulse response of a thick cylindrical shell. Other measurements include retro-reflective backscattering due to Rayleigh waves on objects with corners. Research includes a convolution formulation for objects having variable curvature or truncations and an analysis of the background phase for shells. (B) Wavefields of random caustics produced by reflection--Wavefields were measured for reflection from a randomly corrugated pressure-release surface in water for a range of frequencies of the incident pulse. The resulting wavefields and intensity moments were modeled with catastrophe theory which accounts for the fluctuations due to caustics. Intensity moments greater than the second were proportional to the frequency raised to an exponent (the twinkling exponent). (C) Interaction of sound with sound mediated by a suspension of particles was demonstrated with the probe wave collinear with the standing pump wave. (MM).