Spatial Correlation in Acoustic-Structural Coupling

Abstract

The response characteristics of beams and flat rectangular panels excited by specific acoustic fields were analyzed mathematically. The acoustic-structural coupling coefficients developed by A. Powell and others for general systems were modified and extended to beams and flat rectangular panels with free, simply supported, and clamped boundary conditions. A variable, exponentially decaying spatial-correlation distribution, which allows an analytical approximation of expected near-field characteristics, is an added feature. Numerical results of the acoustic-structural coupling-coefficient frequency spectrum indicate a marked sensitivity to changes in the spatial correlation, a measure of the force-distribution coherence over the structural area. The panel mode shapes progressively lose their wavelength selectivity as the spatial correlation decreases and, hence, respond at all frequencies. An IBM 7090 FORTRAN computer program was written to perform the numerical calculations for single beams and panels with specified boundary conditions and particular plane-wave acoustic fields. An analytical method extending the analysis to an array of beams and/or panels is developed. An approximation for irregular wavefronts is also treated along with the problem of a plane wave traveling at an angle θ with respect to a panel edge and angle φ with respect to the panel plane.