The European AQUO project started in October 2012, in the scope of the FP7 European Research Framework, for three years duration. The final goal is to provide policy makers with practical guidelines and solutions, in order to mitigate underwater noise footprint due to noise radiation from ships. For a maritime area under consideration, mitigation solutions can be split into two categories: the first one is to reduce the underwater noise emission of the noisiest vessels sailing in the area, and the second one is related to ship traffic management. The present paper addresses the first type, and the purpose is to assess the efficiency of different mitigation measures, corresponding to the dedicated task 5.2 of AQUO Project. First, an overview of a comprehensive list of possible mitigation measures is presented. Then, study cases corresponding to reference vessels are defined and several mitigation measures are tested in order to give an estimation of the reduction of ship source level (underwater radiated noise). To achieve this task, different modeling techniques and experimental results from previous tasks of AQUO Project are used. Special care must be taken on the relative importance of the part of radiated noise due to internal machinery and engines, and the part due to propeller(s). The analysis of the result allow identifying the most promising solutions.