Simulation-based analysis of acoustic absorbent lining subject to normal plane wave incidence

The performance of an acoustic absorbent lining can be significantly enhanced by introducing holes inside the lining. Its performance is dependent on the material properties, thickness of layers as well as the size and distribution of holes. In this paper, a simulation-based design approach that combines the acoustic finite element method (FEM) and acoustic duct method (ADM) with a multi-variable optimization technique is proposed for the design synthesis of the acoustic absorbent lining. The proposed method treats a single cell of a periodic acoustic absorbent lining in isolation. The cell may contain a set of holes. Two acoustic ducts are attached at opposing faces of the isolated cell. FEM model is built for the cell and these two acoustic ducts. The reflection and transmission characteristics of acoustic absorbent lining are calculated simultaneously using the acoustic duct theory. The zero-order optimization method is applied to optimize the various design variables, such as Young's modulus of the material, damping loss factors and the diameters of cylindrical holes, etc., to achieve the desirable acoustic performance of the absorbent lining at a single frequency of interest. The proposed method is validated against analytical solutions for a homogeneous acoustic absorbent lining. Numerical examples for the linings with different optimized results are presented to demonstrate the performance of the optimized absorbent lining.