Noise Pollution in the North Sea

The North Sea is one of the busiest seas in the world. All this human activity creates a lot of underwater noise. This can have harmful effects on marine mammals and other organisms in our sea. Fortunately, there are ways to reduce noise pollution.


Infographic: Noise Pollution in the North Sea

Sources of Underwater Noise

Over the past decades, underwater noise from human activities in the Belgian part of the North Sea has increased significantly. The main sources of underwater noise are shipping, explosive ordnance disposal, sonar, the construction of wind farms, and sand extraction and dredging.

  • Shipping: Engines and propellers produce continuous noise that can travel long distances.
  • Explosive Ordnance Disposal: Unexploded ordnance (UXOs), such as those from World War II, are sometimes detonated, causing intense sound waves.
  • Sonar: Sonar is a technique that uses sound waves to measure distances to objects underwater and to navigate. A signal (“ping”) is emitted and reflected by the seafloor and underwater objects. These reflections are used to create a sonar image. The technique is used for military purposes and geophysical surveys.
  • Wind Farm Construction: The piling of foundation structures for offshore wind turbines, in particular, generates intense noise.
  • Sand Extraction and Dredging: During these activities, a vessel uses powerful pumps and a suction pipe dragged across the seabed—like a vacuum cleaner—to extract sand, clay, and silt from the sea floor.

Impacts of Underwater Noise

For many marine species — including marine mammals, fish, and even invertebrates — hearing is a crucial sense. Because there is little light underwater, sound plays a vital role in their survival. Sound waves help them with orientation, communication, finding food, and reproduction. Moreover, sound travels much more efficiently underwater than in air: it is barely absorbed and can move up to five times faster, reaching speeds of up to 1,500 meters per second. An increasing number of studies show that underwater noise has a negative impact on marine life.


Some Key Effects Include:

  • Masking of Biological Signals: Many animals rely on sound to communicate and to understand their surroundings. Human-made noise can interfere with their calls and echolocation (the use of sound waves and echoes to locate objects). This can hinder their ability to find food, reproduce, communicate, and orient themselves.
  • Behavioral Changes: Animals may alter their habits due to noise. They might flee from an area or change their communication patterns, which can impact their chances of survival.
  • Injury and Death: Exposure to loud sounds can cause temporary or permanent hearing damage in marine mammals and fish. The gas-filled swim bladders of fish can also be damaged by extremely high noise levels, such as explosions. In some cases, this can be fatal.

          


Possible Solutions to Underwater Noise Pollution

Underwater noise is a growing problem in the Belgian part of the North Sea. Because sound travels such long distances, it is also a transboundary issue. For this reason, regional cooperation is taking place between various countries around the North Sea. As part of the OSPAR Convention, a Regional Action Plan for Underwater Noise is currently being developed. This plan includes both national and collective actions to reduce noise pollution.
 
There are, in fact, measures available to limit the impact of underwater noise, such as improved ship design, reduced sailing speeds, the use of bubble curtains during piling activities, and the gradual start-up of sonar equipment or machinery used for pile driving.


Poster: How to Reduce Underwater Noise from Ships

  • Improved Ship Design: Innovations such as more efficient propellers, noise-dampening engines, and optimized hull designs can significantly reduce the noise generated by ships. Learn more in this study on reducing emissions and underwater noise from maritime transport. Since 2023, new guidelines have been adopted to limit underwater noise from commercial vessels. These include updated technical knowledge, references to international measurement standards, and tools such as templates for noise management plans. The revised guidelines were developed by the Sub-Committee on Ship Design and Construction of the International Maritime Organization (IMO).
  • Reduced Sailing Speed: Sailing at lower speeds is a simple way to reduce underwater noise, fuel consumption, and emissions. Such a measure must be agreed upon internationally, as a level playing field for all vessels is necessary. Read more in this study on the effects of speed reduction for ships.
  • Mitigating Pile-Driving Noise: Bubble curtains around the pile-driving sites for wind turbine foundations can reduce noise levels. There are also special hammers that push instead of strike, generating less noise.
  • Warning Animals: It is possible to deter animals before they are harmed by (too) loud noise by emitting signals that they dislike. Additionally, loud machinery (e.g. sonar, pile-driving hammers) can be started up slowly, giving animals time to swim away. Human observers can also be deployed to postpone activities if a marine mammal is spotted.
  • Regulatory Framework: Belgium’s Marine Strategy specifies that impulsive sound sources must not exceed a certain noise threshold. In 2024, the European Commission established limits for both continuous and impulsive underwater noise, which Member States must implement further. When evaluating environmental permit applications for offshore activities, underwater noise is assessed as an environmental pressure. Conditions are imposed in the environmental permit to reduce acoustic impact, and continuous monitoring of these activities is essential.

​Order new information materials about noise pollution in our North Sea

The Marine Environment Department (FPS Public Health) and the Shipping Directorate-General (FPS Mobility) have jointly developed a campaign to raise public awareness about underwater noise in the sea. You can order the infographic, poster, and flyer on underwater noise here.

Interesting links related to underwater noise pollution

More information

In 2020, two studies on underwater noise were conducted by the research agency TNO on behalf of the Marine Environment Department of our FPS. You can consult the studies here (full studies in English – summaries in Dutch and French):