Analysis of a perforated panel for the correction of low frequency resonances in medium size rooms

This work illustrates an engineering approach for the analysis of plywood/fibreglass perforated panels, to be used for the linearisation of the frequency response of medium size rooms below 200 Hz. The sound absorption coefficient of these panels is computed, by means of coupled acoustical/structural finite element (FEM) analyses, as a function of the frequency. The comparison between the results given by a complete numerical model of the panel, and those provided by a simplified numerical model, in which only one hole and surrounding material (wood, air, and fibreglass) are described, shows that the second computational approach provides essentially the same results as the former one, at a quite reasonable cost. The FEM results allow us to understand some details about the air motion inside the panel, and to define suitable assumptions for the construction of a simplified analytical model of the panel. Both the numerical and the analytical results are finally compared to experimental data obtained by means of pressure-particle velocity measurements.