Underwater noise measurements with a ship retrofitted with PressurePoresTM noise mitigation technology and using HyDroneTM system

This paper presents the sea trials results by measuring the underwater radiated noise (URN) levels of a research vessel retrofitted with the novel "PressurePoresTM" URN mitigation technology on her propellers to demonstrate the effectiveness of this technology in full-scale. Tip Vortex Cavitation (TVC) is one of the main contributors to a URN. So the strategic implementation of the PressurePoresTM is aimed to reduce the TVC and subsequent URN of ship propellers. During the sea-trials, the URN levels were measured when the vessel's propellers were in the unmodified (without PressurePores) and modified (with PressurePores) conditions, including comprehensive cavitation observations using a high-speed camera to assess PressurePoresTM technology. The trial results showed this innovative technology could mitigate the TVC and resulting URN signature by 10dB. Also, in this measurement campaign, a novel URN measurement method using an aerial drone with a miniature hydrophone called the "HyDroneTM" system was tried successfully. HyDroneTM can be a flexible and practical alternative URN measurement technique to the conventional tethered-based method to improve the undesirable background noise corrections.