Experimental assessment and numerical simulations of marine fouling effect on underwater sound absorption coatings

Abstract

Underwater sound absorption coatings capable of absorbing sound energy is essential to conceal underwater vehicles. While the accumulation of marine fouling on surfaces of ship hulls, platforms, and submarines can significantly alter their acoustic properties. Currently, the precise impact that different stages of marine fouling have on underwater sound absorption coatings remains unclear. In this study, a novel lab assessment method was developed to investigate the acoustic effect of marine fouling on the underwater sound absorption coatings. Four distinct stages of marine fouling were artificial fabricated and characterized, including conditioning film, microfouling, medium macrofouling, and heavy macrofouling. These effects are quantified through comprehensive tests conducted in a water-filled impedance tube. It is found that the first two stages of marine fouling have a negligible impact on the underwater sound absorption performance within the low frequency range of 500 Hz and 2000 Hz. While a limited impact is observed in the frequency range of 2000 Hz–5000 Hz, where the sound absorption coefficient remains approximately 0.6. Conversely, in the third and fourth stages of fouling, the average sound absorption coefficient drops from 0.8 to 0.2. Further, a new acoustic finite element method (FEM) model of hard fouling was developed to predict the acoustic effect, and the numerical results show the same trend with the experimental results. These findings emphasize the importance of considering antifouling strategies during the design of underwater sound absorption coatings, with a particular focus on targeting hard fouling organisms as the primary objective.