A Call to Action to Reduce Underwater Radiated Noise while Reducing Greenhouse Gas Emissions
Authors: Spence Jesse Hunter , Yin Carol 
Published: September 2024

In August 2023, the International Maritime Organization (IMO) issued the Revised Guidelines for the Reduction of Underwater Radiated Noise from Shipping to Address Adverse Impacts on Marine Life (herein, “Revised Guidelines”), which includes guidance that careful consideration should be given to the interrelationships between energy efficiency, greenhouse gas reduction, and underwater radiated noise reduction (IMO 2023). Recognizing that underwater radiated noise from commercial vessels may have negative effects on marine life, especially marine mammals, and that continuous anthropogenic ocean noise is primarily driven by commercial shipping, the Revised Guidelines is part of the IMO’s greater effort to drive the commercial maritime industry towards designing and constructing vessels with lower underwater radiated noise impacts on marine life while also meeting mandatory greenhouse gas emission reduction targets.
Commercial vessels have historically been designed without consideration for underwater radiated noise. This can present challenges for conventional designs to meet the IMO’s goals of reduced underwater radiated noise and greenhouse gas emissions. While some noise control approaches exist that can be easily implemented without significant adverse impacts, there are areas with significant challenges. For example, propeller noise is a primary cause of underwater radiated noise from commercial vessels. Propellers that have been designed to maximize fuel efficiency may not be easily modified to meet all design criteria of reduced underwater radiated noise, reduced greenhouse gas emissions, and other standard vessel design goals. Additionally, for existing vessels, retrofits to achieve underwater radiated noise reductions may be cost-prohibitive; therefore, incorporating underwater radiated noise considerations at the earliest design and construction phases is the best way to ensure the right design approach is applied to lower underwater radiated noise impacts on marine life while also meeting mandatory greenhouse gas emission reduction targets (Spence 2022).
New concepts and design approaches will need to be implemented to meet the IMO’s goals of reduced underwater radiated noise and greenhouse gas emissions. An IMO “Experience Building Phase” of the Revised Guidelines is now underway where, over the next three to five years, lessons on how vessel underwater radiated noise can be reduced will be developed and compiled through technical investigations, studies, and experimentation. Naval architects and marine engineers, as well as academia, shipyards, equipment manufacturers, and others, will play an important role in the future of quiet vessel design. As the commercial shipping industry is currently focused on designing vessels that are energy efficient to meet mandatory greenhouse gas emission reduction targets and optimized for performance at higher speeds to meet customer demands, there are also opportunities for innovative concepts and designs to lower commercial shipping’s impact on anthropogenic ocean noise and overall environmental impact to safeguard our oceans and the diverse ecosystems they support.