No abstract

A statistical energy analysis approach was developed in this paper for the prediction of the sound transmitted through a flexible plate loaded by the turbulent wake of a car rear view mirror. The fluid loading is simulated using a direct noise computation code. This code solves the full compressible three dimensional Navier-Stokes equations with highly accurate space and time algorithms and is able to capture the low amplitude acoustic part of the wall pressure fluctuations. The computed wall pressure field is used as power input in a statistical energy analysis model coupling the flexible plate to an acoustic cavity. Although the acoustic component is of small magnitude compared to the convected component of the fluid loading, it is shown that the non-resonating plate modes provide an efficient transmission path to the acoustic excitation which cannot be neglected below the coincidence frequency of the plate. Above this critical frequency, the sound pressure inside the cavity is driven by the resonant modes and the acoustic component of the wall pressure fluctuation. 2 Nomenclature a M = plate modal displacement  i = internal damping loss factor A = area of the vibrating plate       ij = coupling loss factor c 0 = speed of sound  N = cavity modal damping D = plate bending stiffness  = plate Poisson's ratio e = plate thickness  = spectral density of the radiated power E = plate Young's modulus    = spectral density of the powerradiated by the fc = coincidence frequency of the plate M th mode of the plate k c = convective wavenumber       = plate density k M = wavenumber of the M th plates's mode      = air density    k 0 = acoustic wavenumber  M = modal radiation efficiency L x , L y = plate dimensions        <> = Average radiation efficiency of m s = plate mass per unit area resonating modes p = pressure load on the plate  c = plate's coincidence angular frequency P = acoustic power radiated by the plate   = M th eigenfrequency of the plate P i = external power input  = center frequency of the analysis band P ii = power dissipated in a subsystem P ij = power transmitted from subsystem i to subsystem j P M = modal component of the acoustic pressure load U c = convection velocity v M = plate modal velocity w = plate normal displacement w M = plate modeshape W i