Sound absorption of single- and double-layer microperforated insertion units.

Abstract

Sound absorption by microperforated panels (MPPs) has received increasing attention recently as an alternative in applications with special cleanliness and health requirements. Since the hole diameter-to-panel thickness ratio must be close to unity, MPPs result limp, and therefore difficult to handle for practical applications. Microperforated insertion units (MIUs) were proposed recently to solve this trouble. They combine a millimetric panel with a micrometric mesh to provide an absorption curve similar to that of an MPP. The disadvantage of an MIU, as compared with an MPP, is that its performance depends on the tuning of seven parameters. Furthermore, when a double-layer absorber is required to increase the absorption frequency band, the number of constitutive parameters to be tuned becomes the design rather arduous. Therefore, it could be attractive to know the combination of constitutive parameters, within given variation ranges, which provides the maximum mean absorption for a prescribed frequency band. This is a typical optimization problem. Thus, this paper proposes the application of simulated annealing for optimizing the mean absorption of single- and double-layer MIUs within given variation ranges of their constitutive parameters.