On wave propagation and attenuation properties of underwater acoustic screens consisting of periodically perforated rubber layers with metal plates

The underwater acoustic screens made of periodically perforated rubber layers with metal plates are often used to enhance reflections and reduce transmissions of sound in water, under high hydrostatic pressure. Previous studies have tended to focus on the acoustic response of finite-thickness structures of the screens, rather than on the wave propagation properties of the corresponding infinite crystal structures. In this work, a numerical method, which combines finite element method and the layer-iteration technique, is developed to study the complex band structure of the infinite crystals and the acoustic response of the finite-thickness structures for the screens. Numerical results for the screens with elastic and viscoelastic rubber materials are presented for analyzing the features of propagation modes, band gaps, and attenuation of the waves in the screens. Reflection, transmission and absorption spectra of the screens are compared with the corresponding complex band structure of the infinite crystals in detail for providing a comprehensive understanding of the wave propagation and attenuation properties of the screens.