Sonar Self-noise and Acoustic Transmission of Acoustic Window Made from Functionally Gradient Materials

The sonar self-noise characteristics of an acoustic window made from multilayer functionally gradient materials (FGMs) under external turbulent pulsating pressure excitation were theoretically modeled using the multilayer plate (MLP) transfer function method and the turbulent pulsating pressure wavenumber-frequency spectrum. An MLP transfer matrix was used to determine acoustic transmission loss of the multilayer FGM plate under plane wave excitation. The theoretical model was verified by the finite element method. The FGM was fabricated from rubber and fiberglass-reinforced plastics (FRP)/carbon fiber. The acoustical transmission loss of the multilayer FGM plate and noise reduction patterns of the multilayer FGM acoustic windows were assessed at different gradients. The acoustic effect of the window on external sound waves and its spatial filtering effect on external turbulent fluctuation excitations can be adjusted by regulating the proportions of rubber and FRP, which changes the gradient variation pattern.