Contribution of Antisymmetric and Symmetric Waves to the Reflection of Sound in a Fluid by a Thick, Homogeneous Plate.
NAVAL RESEARCH LAB WASHINGTON DC
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Thick-plate theory, for flexural and extensional waves in plates is applied to the analysis of the reflection of sound from an isotropic, homogeneous plate. An explicit expression is given for the reflection coefficient when both antisymmetric and symmetric waves are contributing to the reflection mechanism. This is compared with the case in which these types of waves are assumed to occur separately. It is shown that the relative strength of the two wave types, as measured by the cross-sectional average of the square of the particle displacement, is strongly dependent on coincidence between the trace speed of the incident wave in the fluid and the free wave speed of the pertinent wave type in the plate. Away from resonances, the energy densities of the two wave types appear to be about equal. This leads to the conclusion that the contribution of symmetric waves to the reflection of sound by a plate should be taken into account. Author