How Improving Energy Efficiency Can Reduce Underwater Noise from Ships

Amy Nugent and Kristin Westdal | December 16, 2025

A recent workshop at the International Maritime Organization highlighted solutions that address both noise pollution and emissions.

Ships play a vital role in connecting people and trade here in Canada and around the world. At any given time, tens of thousands of large vessels are crossing the oceans, with many smaller boats operating around the coasts and ports.

However, all this traffic has an impact. Global shipping is responsible for around 3 percent of planet-wide emissions, more than the aviation industry, and that amount is projected to grow significantly under business-as-usual scenarios. Ships also generate a less visible form of pollution: noise. While they might not seem too obtrusive above the waterline, the sound from engines and propellers radiates out under the waves and has been shown to affect whales, fish, and other animals that rely on the natural underwater soundscape. Noise can cause stress, prevent animals from feeding and communicating, and in extreme cases can even cause injury or death.

What if there was a way to address these problems at the same time? That was the goal of a recent workshop at the International Maritime Organization, where member states met to discuss the results of studies and pilot projects on technologies and ship designs that both reduce underwater noise and improve energy efficiency.

Oceans North attended to share lessons from our underwater noise research in the Arctic and understand current best practices from industry, governments, and environmental organizations for addressing shipping impacts. It demonstrated that there are real-world approaches and technologies—many being piloted here in Canada—that reduce underwater radiated noise, reduce greenhouse gas emissions and air pollution, and improve energy efficiency.

Image – Many animals in the ocean rely on sound to help feed, navigate, and reproduce. Noise pollution generated by ships can cause stress, prevent them feeding and communication and more.

Some of the most exciting projects are happening on the West Coast. As part of its work with the Port of Vancouver, BC Ferries presented a propulsion system retrofit for one of its coastal class vessels, which sail between the Lower Mainland of BC and Vancouver Island.

Their sea trial of a new propulsion system and propeller had dramatic results—a 16-decibel reduction at 13.7 knots compared to the existing system. That might not sound like a lot, but because the decibel scale is logarithmic, it actually represents an exponential decrease in noise, with a sound intensity roughly 40 times less than before. In a corridor where BC Ferries are the most active vessels, the improvement to the soundscape for whales and sea life would be substantial.

The payback period for this technology is also promising. The retrofits provide significant gains in energy efficiency, with fuel savings of 40 percent at a speed of 14 knots—all without impacting sailing times. BC Ferries will have retrofitted all three coastal class vessels by early 2026.

For a congested ocean corridor, these reductions in underwater noise are critical to protecting the sensitive ecosystem and endangered southern resident killer whales, while the improved fuel consumption reduces air pollution and supports human health.

Image – In British Columbia, southern resident killer whales are one of the species impacted by shipping noise.

In addition to retrofitting existing ships, new zero-emission vessels also show promise for tackling these problems. At the workshop, the Canadian naval architects Robert Allan Ltd. presented the results of a test they conducted comparing their battery-electric tugs (now a fleet of five) to diesel-mechanical tugs. The goal was to see how well they reduced emissions and underwater noise, as well as to assess prospects for industry adoption.

The test assessed three operational states: loitering, transiting, and pushing and pulling with thrusters. Unsurprisingly, the electric vessels produced significantly less CO2 (a 99 percent reduction compared to diesel-mechanical tugs). They also performed much more efficiently, with a system energy efficiency of 83 percent during useful work—by comparison, a conventional diesel tug had a 42 percent system efficiency. The electric vessels were 8 decibels quieter in transit and 17 decibels quieter while loitering, although noise increased while pushing and pulling.

The commercial case was more complicated. Because emissions, air pollution, and noise are all external costs borne by people and the environment, they are not always factored into business decision-making. While Robert Allan documented significant fuel savings, they also concluded that the cost of a new battery-electric tug (approximately 70 percent more expensive than a diesel-mechanical boat) remains a significant barrier to broader uptake, even as battery costs continue to come down.

This highlights the important role programs and policies play in incentivizing solutions to reduce pollution and improve public health. Currently, Transport Canada requires large commercial ships to measure and report on their carbon intensity, as well as to develop plans to improve their emissions performance. These rules are not stringent, but they are binding and will create further opportunities to reduce emissions and improve energy efficiency across fleets.

Image – There are real-world approaches and technologies—many being piloted here in Canada—that can simultaneously reduce underwater radiated noise, reduce greenhouse gas emissions and air pollution, and improve energy efficiency. These solutions include retrofitting existing ships and developing new zero-emission vessels.

As for underwater noise, the Government of Canada has no binding regulations. Some marine protected areas—for example, Gwaii Haanas National Marine Conservation Area Reserve—include restrictions on activities such as seismic surveys and underwater blasting. However, these are variable and not consistently supported through regulation and enforcement. The Department of Fisheries and Oceans did release a long-awaited draft Ocean Noise Strategy in 2024, which included support for further research and monitoring but few specifics on management measures. Clear, enforceable, well-monitored domestic standards for energy efficiency and noise pollution would go a long way to advancing Canada’s policy aims in parallel with private-sector innovation.

There are also efforts happening at the global level to address these problems. The International Maritime Organization, which regulates ship owners and flag states, first issued guidance in 2014 on reducing underwater noise. These were then updated in 2023 Guidelines for the Reduction of Underwater Radiated Noise from Shipping to provide more specific technical advice, including on ship design, measurement, and co-benefits with energy efficiency. The IMO is currently in an “experience building phase” of the guidelines and considering how to move forward with enforceable ship design standards. As for improving energy efficiency and reducing emissions, the IMO has already adopted a variety of regulations on fuel consumption and emissions reporting, mandatory energy efficiency management plans, and regulated carbon intensity improvements.

When combined with regulations and incentives, there are several practical solutions that are ready to be deployed that address both underwater noise and emissions while lowering fuel costs. These range from new and emerging technologies highlighted in the workshop—retrofits, zero-emission vessels—to more basic but no less important ones, such as reducing vessel speed, or even new versions of old ideas, such as wind-assisted propulsion. It was exciting to witness Canada’s leadership in this space.

At the same time, improving energy efficiency will not solve all the problems associated with underwater noise. To protect sensitive habitats and marine protected areas, there is still a need for activity and vessel-specific regulations, as well as regional and seasonal noise thresholds in certain areas. Oceans North urges the Government of Canada to place a high priority on developing binding underwater noise limits for these places, and to work with Indigenous peoples who are already monitoring and managing their waters.