Underwater Absorption Performance of a New Rubber-Based Acoustic Absorber Embedded With Composite Scatter

Abstract The acoustic impedance of rubber matches well with that of water, which makes rubber have a good performance for absorbing underwater noise. However, the effective absorption of underwater low-frequency sound is still a challenge. To solve the problem, a new rubber-based acoustic structure is proposed. Based on the coupling effect between cavity resonance and local resonance, the structure can effectively control the propagation of elastic waves. The absorption coefficient and displacement field distributions of the cavity-type structure, local resonant structure, and the proposed structure are compared to explain the energy loss mechanism. The material parameters of the proposed structure, such as the density of the inner hard core, and elastic modulus of soft rubber and rubber matrix, are changed to investigate the influence of material on absorption performance. In addition, the geometry shape of the cavity is varied, cone cavity and circular truncated cone cavity are introduced to analyze the influence of shape on absorption performance. The results show that the existence of the cavity enlarges the interaction effect between the hard core and soft rubber and increases the displacement of the rubber matrix in the vertical direction. The reduction of the elastic modulus of soft rubber and the increase of density of the hard core can improve the absorption coefficient. The cavity should be designed to be gradient to enhance the coupling effect to dissipate underwater low-frequency noise.