Analysis of decoupling mechanism of an acoustic coating layer with horizontal cylindrical cavities

Introducing the decoupling coating is an effective way to reduce sound radiation from underwater structures. In order to investigate the decoupling mechanism of a viscoelastic coating layer with horizontal cylindrical cavities, such a coating layer is approximated to a homogeneous layer with equivalent material properties, and a theoretical model is also developed to predict the sound radiation from a finite plate with such a decoupling coating layer. #br#The validity of the theoretical model is confirmed by comparison with the finite element method; and the decoupling mechanism of the coating layer is discussed. Numerical analysis shows that: (1) The energy flow across the interface between the plate and coating layer is mainly conveyed by longitudinal waves. (2) At a low frequency, the coating layer has nearly no decoupling effect. (3) In contrast with a homogeneous coating layer, the coating layer with horizontal cavities can greatly enhance the mechanical impedance in the mid- and high-frequency areas; hence the mean square velocity is effectively suppressed in the same area. (4) Compared with the homogeneous coating layer, the coating layer with horizontal cavities has a larger impedance mismatch with water, thus it exhibits great vibration transmission loss. Therefore, in general, the coating layer with horizontal cylindrical cavities has a better decoupling performance than the homogeneous coating layer in the mid- and high-frequency areas.