The design of innovative metamaterials with robust and reliable performances is attracting increasing interest in shipbuilding, due to the potential and versatility of these materials. In particular, soundproofing is becoming an even more important characteristic, to ensure the comfort levels required by the standards on board ships. Thus, shipyards are constantly looking for innovative solutions to improve the insulation between environments, while respecting the safety regulations with which the materials on board must comply. In this study, an innovative solution called the Metasolution is designed and characterized, considering both the transmission loss (TL) and the fire resistance. The Metasolution is proven to be a valid substitute for the traditional honeycomb panels used on board for soundproofing. The TL of the innovative solution is increased, and the thickness is decreased, while maintaining the cost and the weight in line with the traditional solution. Moreover, the regulations regarding fire safety on board are satisfied.

The even more restrictive regulations imposed on chemical and acoustic emissions of ships necessitate the installation of after-treatment systems onboard. The spaces onboard are limited, and the Exhaust Gas Cleaning Systems (EGCSs) have big dimensions, so an appropriate integration and optimization of EGCSs allows to save space and comply with international regulations. Moreover, in the available literature, there is a lack of guidelines about the design of integrated EGCSs. This study aims to develop an ad hoc optimization methodology that uses combined Computational Fluid Dynamics (CFD)–Finite Element Method (FEM) simulations, surrogate models, and Genetic Algorithms to optimize the acoustic properties of EGCSs while considering the limits imposed by the efficiency of chemical reactions for the abatement of NO_x and SO_x. The developed methodology is applied to a Diesel Oxidation Catalyst (DOC), and the obtained results lead to a system that integrates the silencing effect into the DOC.