Development of a design procedure for the prediction of structure-borne noise generated by the reciprocating machines installed on board ships

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Reciprocating machines are prominent sources of vibration and structure-borne noise on board ships. The vibrational energy generated by reciprocating machines, in the low and high frequency range, is transmitted through ship structures to accommodation decks, decreasing the comfort level for passengers and increasing the exposure to noise and vibration of crewmembers. Moreover, the vibrational energy transmitted through ship structures translates into underwater noise, affecting the acoustic signature of navy ships and increasing the underwater noise pollution that affects sea life. In order to isolate the sources from ship structures, engines and auxiliary machines are usually resiliently mounted. This solution decouples the source of noise and vibration from ship structures and decreases the vibrational energy transmitted by the sources to the receiving structures. Even though this solution is widely accepted and used, a proper design of the decoupling system and its practical application is more complex. An effective design of the coupling between the source and the receiving structures should take into account the dynamic characteristics of the source, isolating system, and receiving structures, as well as the interactions among these parts. To date, classification society rules and international standards provide the designers with effective procedures for the design of the decoupling between reciprocating machines and receiving structures, in the dynamic point of view, solely in the low frequency range. Regarding the structure-borne noise level, no effective procedures are available for its prediction, nor are any standard limits provided. This proposal investigates the development of a new design procedure for the prediction of the structure-borne noise generated by reciprocating machines on ships. This procedure will be based on numerical models and analytical formulations. A new mock-up will be created at Memorial University. The mock-up will reproduce the typical structures of a marine diesel engine foundation and experimental tests will be carried out to validate the numerical models and the effectiveness of the analytical formulation. The design tools that will be developed in this research activity aim at ship designers and ship consultants. Using these tools, they will be able to predict the structure-borne noise generated by reciprocating machines in the early phases of the design of a new ship, identifying effective solutions to reduce the overall on-board noise level. This will increase the comfort for passengers, decrease the exposure of crewmembers to hazardous levels of noise, and allow the designers of navy ships to control the acoustic signature of the vessels.