Geometrical Aspects of Scattering and Physical Effects of Sound.
1997
Marston, Philip L.
Research is reported in the following areas: 1 Transient and high-frequency enhancements of the scattering of sound by elastic objects in water are measured and analyzed. (The impulse response of a thick cylindrical shell in water was measured as a function of aspect angle. The measurements show the frequency locus of a backscattering enhancement extending to near end-on incidence in agreement with predictions for an antisymmetric leaky Lamb wave. Other enhancements and supporting theoretical developments are noted.) 2 New measurements and theoretical work on the interaction of sound with sound mediated by an aqueous suspension display coherent scattering effects for a range of conditions. 3 The coupling of an oscillating magnetic field to the quadrupole quasi-flexural mode of a shell in air is investigated. (An acoustic signature produced by shell vibrations in response to an oscillating Maxwell stress is easily detected even without the static bias magnetic field normally used in an EMAT.) 4 An oscillating electric field is used to excite the monopole mode of bubbles in an insulating liquid. (As with item (3), the method may be useful for measuring mode frequency and damping where exact solutions are not known.)
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