THE EFFECT OF FLOATING DECK STRUCTURES ON UNDERWATER RADIATED NOISE

A concept for underwater machinery noise mitigation of future civil and military ships is the application of a common deck structure, supporting multiple machines, which is installed on resilient mounts on the ship's foundation structure. TNO is addressing the availability and testing of tools to be able to set realistic targets for the radiated noise signature and to verify future vessel designs against these targets. The TNO Assessment Model for Radiated Underwater Sound (AMRUS) is a semi-empirical prediction tool to predict separate contributions of different resiliently machinery noise sources to the underwater radiated noise at far field locations. It is a compilation of measured machinery source acceleration levels, mounting transfer and ship transfer functions, which are present in a large database. Until recently, the effect of resiliently mounted ('floating') deck structures on machinery noise transmission was not included in AMRUS. To be able to the support the complex design process of a floating deck, a formulation of the deck mount transfer function has been derived. For that purpose this formulation is split into the separate deck structure input and transfer mobilities, which can serve as acoustic indicators for a specific deck design during the specification, design and building phases. The formulation can be used to assess global design parameters of a deck in an early design phase, but can also serve as a base for finite element model results to determine the mount transfer function for a more detailed deck design. ANV; Cirrus Research Plc; Orion