# Canada’s Efforts to Mitigate Underwater Radiated Noise

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In the dark undersea world, sound is essential. For marine life, sounds often play a crucial role in communication, foraging, reproduction, and navigation. However, as human activity in the oceans increases, so does underwater noise. Various industries contribute to ocean noise—offshore energy, construction, military operations, and of course vessel traffic. The noise generated by vessels is referred to as underwater radiated noise. With growing activity from commercial shipping, offshore developments, fishing and recreational vessels, underwater radiated noise pollution is increasing.

This increase has serious consequences for marine life, particularly species that rely on sound to survive, such as marine mammals. Underwater radiated noise can mask natural sounds, which may make it difficult for individuals to communicate, find a mate or prey, or even avoid predators. Some may change their behaviours, such as communicating less or avoiding or abandoning important habitats. Underwater radiated noise may also increase stress and cause other health problems.

Addressing underwater radiated noise is gaining attention. On the international stage, the International Maritime Organization updated its non-mandatory guidelines on reducing underwater radiated noise in 2023. In Canada, the federal government is developing an Ocean Noise Strategy to enhance the science, knowledge gathering, innovation, assessment, and guide management of underwater radiated noise while raising awareness of the issue.

What is sound, and how does it travel through water?

Sound is a form of energy created by vibrations. When something vibrates, like strings on a guitar or a car engine, the surrounding molecules also vibrate and bump into their neighbours, which bump into their neighbours, creating sound waves. These waves travel outward from the source in all directions. If the sound waves reach a receiver – like your ear – before they lose too much energy (and if the waves are within your hearing range), they are interpreted as sound.

Sound can be described by its amplitude (how loud) and frequency (high or low pitch). To human ears, larger amplitude is perceived as a louder sound. Amplitude generally decreases with distance travelled, which is why sounds from a source far away are quieter than those close by. Frequency refers to the number of cycles of a sound wave in a given time period. The more sound-wave cycles that occur a time period, the higher the frequency. Low-frequency sounds, like a foghorn or blue whale call in deep water, travel farther than high-frequency sounds because they lose less energy over distance.

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When in water, sound travels faster and farther than in the air because the different physical properties of water mean it is denser than air and can transfer energy faster. Ocean conditions influence how far and how fast sound travels. Sound travels faster at higher water temperatures, salinity levels (saltiness), and pressure. Temperatures drop and pressure increases with greater water depth, meaning sound can travel at different speeds depending on depth.

Water depth is also significant because of sound attenuation. When a sound wave reaches the sea surface or seafloor, sound energy can be absorbed or reflected and refracted (bounced around), reducing the intensity of acoustic energy. The type of seabed material influences the amount of energy loss. For example, sand tends to absorb more sound than rock. In the Arctic, ice cover both absorbs and reflects sound, depending on the smoothness of the ice. For these reasons, a sound wave could travel farther and faster in one location than another. Even in a single area, how sound behaves can change from one day to the next.

Underwater sound is considered to be noise when it is generated by human actions (also referred to as anthropogenic noise), transmitted below the surface of the water and has a range of impacts on marine animals. Underwater noise can be continuous and long-lasting (like a ship propeller) or impulsive with an instantaneous start and stop (like a seismic survey air gun or echosounder).

Image source: Fisheries and Oceans Canada, About ocean noise and its impacts

The need to mitigate underwater radiated noise to protect marine ecosystems is gaining attention and urgency. Canada’s approach to reducing underwater noise includes supporting voluntary and mandatory operational measures (e.g., vessel seasonal slowdowns), and since 2017, promoting quieter ship designs through the International Maritime Organization. Canada’s efforts led to the adoption of updated guidelines on reducing underwater radiated noise in 2023. To support these revised guidelines, the International Maritime Organization also approved an underwater radiated noise Action Plan with an experience-building phase for different countries and international organizations to share best practices to address underwater noise. Further, the Canadian federal government is developing an Ocean Noise Strategy to enhance the science, knowledge gathering, innovation, assessment, and management of underwater noise while raising awareness of the issue.

Learn more about Canada’s Ocean Noise Strategy+

The Government of Canada has key responsibilities for assessing and managing the impacts of human-generated underwater noise in the ocean. With the goal of undertaking a more coordinated and proactive approach to address this complex issue, federal departments and agencies have worked together to develop the first draft of Canada’s Ocean Noise Strategy. This strategy will guide future efforts to address human-generated underwater ocean noise.

The Ocean Noise Strategy includes three main themes:

 Science, knowledge gathering and innovation


 Assessment and management


 Communication, coordination and engagement



The draft strategy was shared with the public in 2024. Feedback received during the consultation process will guide the development of the final strategy and a draft Federal Action Plan on ocean noise. These documents are anticipated to be released in 2025 with additional consultation and engagement on the action plan and its implementation. These processes will involve seeking input from partners and stakeholders to ensure comprehensive and well-informed decision making.

In response to these concerns, Transport Canada’s Quiet Vessel Initiative (QVI) is stepping up to help reduce underwater noise, aiming to reduce noise at the source. QVI provides federal funding for research and development projects to develop and test promising technologies, vessel designs, retrofits and operational practices to make vessels quieter and more efficient, contributing to the protection and recovery of the marine environment and endangered marine mammals. This series of articles explores the results and shares the challenges identified by some of the QVI-funded projects.

How quiet do ships need to be?+

Understanding how ships generate noise, and how much noise they produce, is essential to achieve a quieter ocean. In Europe, mandatory limits on underwater noise came into effect in March 2024. These limits apply to both short-term and continuous underwater noise sources and were created by a technical working group in 2022 to create more tolerable marine habitats.

At home, Transport Canada is working with science and industry partners to establish Underwater Vessel Noise Reduction Targets. These targets are a critical step towards the development of Underwater Noise Management Plans, which will enable vessel owners and operators to take concrete actions to reduce their noise footprints. Government is working in partnership with domestic and international shipowners to develop and implement real-world underwater noise management planning, including testing out Underwater Vessel Noise Reduction Targets. These efforts will inform national and international policy development, contributing to the International Maritime Organization’s experience-building phase to address underwater noise.

This article is part of a five-article series on technology for detecting and analysing underwater vessel noise.

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Continue learning about the new discoveries and challenges in making vessels quieter with the other topics in this series here

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The Quiet Vessel Initiative is a federally funded program through Transport Canada. Industry partners and researchers interested in potential research and development collaborations to advance innovative solutions in marine technology are invited to contact the Quiet Vessel Initiative team at Marine-RDD-maritime@tc.gc.ca.

Featured image credit: Erik Mclean via Unsplash