Sound absorption performance of layered micro-perforated and poro-elastic materials

A sound absorption study has been performed using a micro-perforated panel and a porous layer to investigate, predict, and optimize the acoustic performance of the layered system. The micro-perforated panel flow resistance is modeled by Maa’s equation that combines a rigid panel, where no panel motion is considered, or a membrane to account for mass inertia, showing the potential benefit in sound absorption. Parametric studies demonstrate changes in maximum absorption frequency and amplitude resulting from changes in key micro-perforated panel geometry, e.g., hole diameter, hole thickness, and surface porosity. The ratio of hole diameter to thickness and surface porosity can be effective in controlling the lower frequency range without a large increase in the air depth of the layered system. The micro-perforated panel is also formulated with the porous layer based on Biot theory to investigate the effect of porous materials in a multi-layer system. The sound absorption of a multi-layer combining the micro-perforate and poro-elastic system is shown to be dependent on the resistive property of each layer.