Resonant and non–resonant transmission of random noise through complex plates

An approximation is developed for the transmission of random noise through a finite panel of fairly general type that might be anisotropic or might consist of several layers of elastic materials. The analysis is based on the premise of small values for the acoustic wavelengths and for the fluid loading. The forms of the results are different in various frequency ranges. In particular, for frequencies less than a critical value, a prediction is made for the so–called ‘non–resonant’ part of the power flow: this corresponds to the surface modes that have relatively small (off–resonant) amplitudes but which have supersonic phase speeds. The results have quite general applicability and details are given for a particular anisotropic panel, with results compared with experimental data.