Homogenization of an acoustic coating with a steel backing subject to an obliquely incident sound

An effective homogenization model for the acoustic coating of underwater structures is important for reducing the complexity of acoustic scattering computation, which arises from the huge difference in scale between the integral structure and the inhomogeneous microstructure of the coating. The main difficulty of this homogenization arises from the oblique-incidence effect of external sound waves and the interface effect between the coating and backing. In this work, a hybrid method, combining the Bloch wave analysis and retrieval technique, is proposed to characterize the acoustic behavior of the voided coating backed with a steel plate under the action of external sound waves with an arbitrary incident angle. The effectiveness of this method is validated by numerical simulations and comparison with the Bloch wave method and the traditional retrieval method. The influence of the shear-wave effect under obliquely incident sound waves and the coupling effect between the coating and the backing on the homogenization model is investigated in detail, providing a comprehensive understanding of the effective acoustic behavior of the coating.