Accurate Designing of Flat-Walled Multi-Layered Lining System Using Genetic Algorithm for Application in Anechoic Chambers

Abstract

In anechoic chambers, the flat-walled multilayered acoustic lining systems are cheaper and easier to install than conventional wedge type systems. Sequence, material and thickness of layers are all design variables. By choosing the right configuration, the acoustical performance and overall thic- kness of flat-walled multilayered systems can be comparable to conventional wedge systems. In this study, the materials considered include air and poroelastic materials such as polyurethane foams, melamine foams, and glass wool. In order to evaluate acoustical performance of a given configurati- on, the poroelastic materials are modeled using Biot’s formulations instead of a simpler impedance method to get more accurate results. A genetic algorithm implemented within ModeFRONTIER opti- mization software was used to select configurations which have a cut-off frequency of 100 Hz or less. The configuration that met this requirement with the smallest overall thickness was determined optimal. This configuration has an overall thickness of 65.8 cm and is composed of 4 different polyurethane foams. Since a considerable difference was observed between the cut-off frequencies obtained using Biot’s model and the simpler impedance method, this justifies the use of Biot’s model in the optimization.