Integrated prediction and assessment of underwater noise for commercial vessels

• Main Author: Kellett, Paula Mara Grinbergs
• Published: University of Strathclyde 2014
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.667579

The main aim of this study is to address the need for a commercial ship underwater radiated noise prediction and assessment methodology that could be used in the early stages for new designs. A detailed literature review of current state of knowledge on ship underwater noise sources and potential impacts is carried out. This review also looks in detail at the available noise prediction and propagation techniques, to assess their suitability for use in early stage design. The review also focuses on the related areas of underwater ambient noise, and ship noise regulation and reduction. Following this, a numerical approach for commercial ship noise and propagation prediction is proposed and tested a case study vessel. Field measurement data for the vessel is used to validate and test the approach, and several variations. Some investigation is also carried out for the prediction of machinery noise tonal frequencies. Suggestions are provided for the use of empirical approaches where use of the numerical approach is not viable or appropriate. Impact assessment of the predicted spectra is then addressed. An assessment tool is developed, with several key purposes. Firstly it allows input of key vessel, propeller and machinery parameters to allow empirical prediction of spectra and overall noise levels, and machinery tonal frequencies, which can be compared to predicted or measured spectra. Secondly, an extensive database of marine wildlife species, their conservation status, typical habitat regions, hearing and vocalisation frequency ranges and recorded responses to ship noise, has been compiled. The tool allows this to be filtered or highlighted by operational area, conservation status and frequency range, so that those species which are likely to be affected by a particular vessel can be identified. The potential impacts can thus be assessed in a goals-based approach. Thirdly, the predicted, estimated or measured spectra can be compared with existing regulation and suggested threshold noise levels for a more rules-based approach to impact assessment. Use of these impact assessment approaches are demonstrated using a case study of one of the vessels. Finally, some discussions and conclusions on the main findings of the work are presented.