SPATIALLY LOCALIZED RANDOM FORCING OF FLUID-LOADED ELASTIC PLATES

The response of a fluid-loaded, linearly elastic plate to a spatially localized, random forcing and the radiation of sound therefrom is formulated in terms of two-point coherence functions. Emphasized is the use of linear-phased arrays, of displacement meters on the surface of the plate and of hydrophones located in planes removed from the plate, in an envisioned model experiment. The formulation shows the total experiment to be described via an ordered sequence of operators, termed propagator/filters. Analytic and numeric investigation of these operators are accomplished for ''typical'' experimental scenarios. Of particular interest is the complicated manner in which the ''potential for interference'' of widely separated, in physical or in spectral space, components of an acoustic signal is accommodated in a coherence function formulation. This potential renders a Wigner function, a transformed coherence function, description of a phase space, somewhat inconvenient for discussing the propagation and scattering of deterministic signals. Randomness, which typically eliminates this potential for interference, can make for a convenient Wigner function framework.