Modelling the propagation of underwater acoustic emissions for condition monitoring of marine renewable energy

Marine Renewable Energy (MRE) has progressed towards commercialisation over the recent years but significant barriers still exist including the currently high cost of energy. A significant proportion of this cost comes from Operation and Maintenance activities which can be reduced through the use of condition-based maintenance scheduling. In offshore environments, the submerged location of most devices enables the use of underwater Acoustic Emission (AE), a new condition-monitoring technique. It combines underwater acoustics with AE condition monitoring as used in air. This paper assesses the practicality of such an approach in complex ocean environments through detailed sound propagation modelling using the propagation model Bellhop in the Matlab toolbox AcTUP. Results show that acoustic propagation is very sensitive to variations in the shallow water environments considered. Associated to the shallow depths, environmental variations mean that some frequencies cannot be back-propagated easily, generally limiting access to the monitoring of Received Levels. The results presented here are the first steps toward optimizing AE sensor positions and AE measuring strategies for arrays of devices.