Energy efficiency and URN of a ship – online monitoring onboard

An IMO Expert Workshop on the relationship between Energy Efficiency and Underwater Radiated Noise was held in September 2023. One aim was to discuss the co-benefits between increasing energy efficiency (EE), reducing greenhouse gases (GHG) and reducing underwater radiated noise (URN), and to discuss various measures such as propeller optimization or energy-saving devices. Online monitoring onboard of ships, which constantly monitors the acoustic signature/state of the ship, can be a decision tool for the acoustic emissions (e.g., cavitation is strong, weaker, not present) and therewith help e.g., to determine an acoustical optimized route or distinguish acoustical worse operational conditions. Some classification societies have already established assessment principles in their guidelines to be able to carry out quantitative URN assessments with onboard sensors. Permanent monitoring systems for acoustic signatures have been established for decades in non-civil and research applications and will be provided for civil shipping in the future.