This paper discusses the acoustic mitigation properties of an air–water mixture excited by a monopole source. The numerical study reproduces a flat plate immersed in water and covered by an air film, acting as a sound barrier. This configuration mimics a mitigation device potentially in use for ship noise reduction, considering the flat plate as archetypal of a portion of the ship hull that works as a non-negligible scattering surface. The film, in this case, may also be used as an isolator with respect to the noise produced by the engines operating within the hull and propagating in the water. The study uses a homogeneous mixture model to reproduce the fluid dynamic field of air injected into the water. Once the air–water mixture is fully developed, the density and speed of sound distributions are extrapolated and used as input parameters for the acoustic propagation model. The monopole source exits the mixture layer, and the attenuation properties are assessed by recording the time signal on a probe positioned on the reflecting wall. The results show the difference in the transmission of acoustic pressure considering different frequencies and distributions of the mixture. These findings have significant practical implications, as they demonstrate how the air film can effectively attenuate the signal, with the mitigation effectiveness varying with the source's frequency and the distribution of the mixture of air and water in space.
