Low-frequency broadband absorption of semi-active composite anechoic coating with subwavelength piezoelectric arrays in hydrostatic environments

•A novel global four-terminal network model is proposed for the first time.•The phenomenological theory is developed to predict finite deformations.•The present semiactive coating breaks the traditional lower limit of low-frequency.•Distributed resonant modes are proposed to extend the upper limit of low-frequency. Considering the influence of hydrostatic pressure on geometric parameters of a lining, this paper first proposes a complete global four-terminal acoustic theoretical prediction method based on phenomenological theory for a semi-active composite coating with subwavelength piezoelectric arrays in deep-sea environment, aiming at exploring the energy dissipation mechanisms and broadening the low-frequency sound-absorbing bandwidth. The Neo-Hookean material model is incorporated into the phenomenological theory to analyze the finite deformation of rubber layers under hydrostatic load. Then, the global acoustic model is established by combining the effective medium method, shunt damping technique, and wave propagation theory in layered media. Moreover, the degraded validations are developed by FE simulation and hydroacoustic impedance tube experiment, and the influences of submergence depth and shunt circuit on the absorption characteristics are explored theoretically. It is expected to break the lower limit frequency of low-frequency sound-absorbing from 500 Hz to 200 Hz, and to expand the upper limit frequency thanks to the multi-modal resonant energy consumption mechanism of distributed circuits.