This ICS sponsored study highlights the significant synergy between the implementation of energy efficiency strategies and the reduction of URN. For example, the results suggest that reducing vessel speed by 20% can lead to a significant 6 dB decrease in underwater radiated noise (URN) in fixed-pitch propeller vessels. Wind-assisted propulsion systems have the potential to reduce URN by up to 10 dB, while air lubrication systems can achieve even greater reductions, surpassing 10 dB in URN reduction. Considering the aging fleet of vessels and the forthcoming, more stringent Carbon Intensity Indicator (CII) requirements, the study anticipates a growing trend of vessels implementing energy-efficiency measures to align with the IMO’s revised GHG strategy targets.

The study concludes  that compliance with the IMO GHG regulations could indeed lead to a reduction in URN from commercial vessels, contingent upon the chosen pathway and strategy for meeting the IMO’s revised GHG strategy.

The study identifies the goals advocated for by the Okeanos Foundation, as currently the only global targets for URN reduction that have been proposed.  In consideration of these,  the study concludes that by leveraging the synergies between energy efficiency and URN, accomplishing a 3 dB reduction in shipping’s contribution to ambient noise within a decade is a feasible goal, e.g., through speed reduction. The addition of other efficiency measures (e.g., either air lubrication or wind assisted propulsion) could provide the necessary further reductions to also put the 10 dB within 30 years goal within reach.