Numerical study of the acoustic properties of micro-perforated panels with tapered hole

Micro-perforated panel (MPP) absorbers, well known as a basis for the next generation of sound absorbing materials, are now being widely used in noise control engineering. In order to design the structural parameters of MPP absorbers according to the actual demand, a straightforward method to predict the absorption performance of such absorbers is needed. However, traditional predicting methods, such as equivalent electric-acoustic circuit method, the transfer matrix method, modal analysis method and so on, are based on analytical solution. The use of these methods not only requires development and application of special techniques, but also is not suitable for MPPs with irregular-shaped holes, such as tapered holes which can be used to improve the sound absorption performance of a thick MPP absorber. In order to overcome the problem, a numerical procedure based on finite element method (FEM) is developed to obtain the specific acoustic impedance of an MPP. Using this method, the acoustic performance of MPPs with tapered holes as well as the effect of various parameters on their normal incidence absorption performance is numerically investigated and the findings are useful to guide the structural design.