Broadband underwater sound absorption and performance optimization of a lightweight pressure resistance coating

Abstract To satisfy the requirements of underwater vehicles in large depths and high stealth performance, this paper proposed a lightweight pressure resistance coating designed by micro floating raft arrays. Based on the effective medium method, the coating is subjected to layered equivalent, and a theoretical calculation model for its sound absorption coefficient (SAC) is established. Moreover, the influence of coating parameters on its SAC is explored. The results indicate that the coating parameters have varying effectiveness on SAC and its corresponding frequency position, with Young’s modulus, Poisson’s ratio, loss factor and intermediate mass width having a particularly significant impact on SAC. Afterwards, the genetic algorithm is used to optimize each layer of the coating, resulting in an average SAC of 0.9127 in the range of 10 Hz–30 kHz and maintaining a quasi-perfect sound absorption state of 0.95–1 in the wide frequency range of 10–30 kHz. It is worth noting that the SAC is higher than 0.5 at frequencies above 0.72 kHz, while the thickness of the coating is only 1/52 of the corresponding frequency wavelength. Additionally, the coating’s average sound absorption performance is better than that of a homogeneous layer with the same thickness, but its mass is only about half that of the homogenous one. Furthermore, the coating can maintain over 80% of the high-efficiency sound absorption effect under 0°–60° sound wave incidence angle and hydrostatic pressure within 10 MPa. Overall, this paper provides a potential approach for the pressure resistance and lightweight design of anechoic coating.