Theoretical and experimental calculation of underwater acoustic insertion loss of monolithic panels

Abstract Underwater insertion loss of a material is a key parameter for many applications where acoustic requirements exist. Typically, environmental noise control and mitigation or SONAR are disciplines commonly demanding the knowledge of insertion losses of the material used for such purposes. Materials selected for these applications usually have good structural properties but also are lightweight and have good corrosion behavior and specific acoustic performances (e.g. baffling, transparency). In this sense, glass-reinforced plastics, as well as carbon fiber materials, synthetic or natural rubbers, urethane compounds, etc. are, more and more, part of tailored underwater structures, pods, covers, or acoustic windows. In this work, the underwater acoustic insertion losses of monolithic and isotropic typical panels are theoretically calculated and properly validated via measurements for a wide range of frequencies (10–60 kHz) and angles of incidence (0–80°). The theoretical calculation is carried out through the model proposed by G. Roche and based on the Brekhovskikh formulation, which is implemented within an ad hoc software tool developed by the authors (Sailor). The measurements were performed by the Centro Tecnologico Naval y del Mar – Marine Technology Center (CTN) in a freshwater-calibrated pool/tank located in the town of Cartagena (Spain). The results reveal a solid agreement between the measurements and the simulations carried out with the Sailor software, therefore validating the model proposed by Roche and shedding new light on a field where, to the best of the authors’ knowledge, previous investigations were scarce or lacking.