FLOW NOISE RADIATION CHARACTERISTICS OF ELASTIC PLATES EXCITED BY BOUNDARY LAYER TURBULENCE.
Final rept. 1 Oct 66-31 Mar 68,
CAMBRIDGE ACOUSTICAL ASSOCIATES INC MA
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The investigation treats the problem of sound radiated by an elastic plate, set in an infinite rigid baffle, which vibrates as a result of a turbulent boundary layer pressure field flowing past it. A large highly damped plate can be considered as effectively infinite in determining its response. For such a plate the effects of fluid loading are taken into account. The far-field mean square pressure spectral density is determined for each of three models governing the plate response. These are 1 the classical plate equation, 2 the Timoshenko-Mindlin plate equation, and 3 an orthotropic plate equation. For frequencies above coincidence, the radiated pressure spectral density becomes highly directive at certain well defined angles yielding a directivity pattern reminiscent of rabbit ears. For far-field points lying on a normal to the plate through its mass center the mean square spectral density for each of the models considered becomes independent of the elastic parameters of the plate and depends only on the plate area and its mass per unit area. Author