Noise radiation of an elastic plate excited by turbulent boundary layer pressure fluctuations

A unified theory for calculating the noise radiation of an infinite elastic plate excited by turbulent boundary layer pressure fluctuations is presented. Using the wavenumber frequency transfer function to describe the whole system consisting of the plate and the liquid loading, a general expression of the cross spectrum was derived. It is an integral in the complex wavenum-ber plane and leads to a sum of the residues at the poles of two types. One pole introduced by the convectivc ridge of pressure fluctuations yield a direct transfer component, which is an evanescent wave in liquid because the pole lies in the high wavcnumber region. The poles introduced by the transfer function of the structure produce the radiation field components with the resonance modes of a liquid loaded plate. The pole positions and their residues can be computed approximately by use of the Resonance Scattering Theory. For the case of hydrodynamic noise, in which the range of the frequency-thickness product of interest is relatively low, the symmetric zero-order mode dominates the noise radiation.