The Flanders Marine Institute (VLIZ) has launched a unique underwater sound library for the North Sea. With more than 2000 sound clips, this collection offers insight into the complex soundscape of our busy sea. The library highlights trends across different years and variations between locations. In doing so, the platform supports policymakers, researchers, and the wider public in understanding the impact of both human-made and natural sounds on the marine ecosystem – while also opening up new opportunities for AI-driven research. Moreover, research into underwater sound makes an important contribution to the goals of the recently adopted European Ocean Pact.
In water, sound travels much greater distances than light, making it an essential tool for many marine animals to interact with their environment or to communicate with one another. All the sounds in the marine environment together form the 'soundscape' – a landscape as rich as it is complex.
Natural sound sources can be abiotic (geophony), such as rain, waves, or sediment transport, or biotic (biophony), such as fish sounds or echolocation from dolphins and porpoises. Human presence at sea is ubiquitous and introduces additional sounds (anthropophony) into the environment. With growing activities such as shipping, seismic exploration, and offshore energy production, noise levels continue to increase. In the North Sea specifically – a shallow and heavily exploited sea – the mixture of all these sound sources makes it challenging to analyze and interpret the soundscape.
A solid understanding of underwater sound at sea is anything but a luxury. The European Union recognizes sound as a key environmental factor. Under the Marine Strategy Framework Directive (MSFD), underwater sound is one of eleven parameters that determine the 'good environmental status' of seas and the ocean. For the North Sea, a threshold has been set at 100 decibels (comparable to the noise of a jet aircraft at 300 meters height). Limiting the sound level in the North Sea to this threshold is therefore crucial to achieving good environmental quality.
To better understand sound in the North Sea, the different sources and how it evolves over time, VLIZ has now launched a scientifically grounded library containing 2000 sound signatures – with the potential to grow to 100.000 clips in the future. The sound library consists of a website and an underlying database architecture. To build the collection, VLIZ conducted additional field recordings of the underwater soundscape under varying conditions. The institute operates an active monitoring system that records underwater sound semi-continuously at fixed locations.
But the underwater sound library is more than just a collection of sounds from different sources. The platform also enables users to visualize trends in underwater sound, cluster sounds based on their frequencies, and serves as a foundation for training machine learning models to automatically process acoustic signals, develop automated applications, and enable new research. In addition, the library’s database architecture allows sounds to be linked with other relevant data, such as AIS data on shipping activity, seabed information, animal presence, wind speed, and more.
As a next step, VLIZ aims to connect the library of underwater sounds with the Global Library of Underwater Biological Sounds (GLUBS), thereby contributing to a greater global understanding of both known and unknown sounds. In doing so, it provides researchers with the datasets and tools needed to study the marine environment.
The sound library for the Belgian part of the North Sea was developed by VLIZ with the financial support from the Flemish government, through the office of Jo Brouns, Flemish Minister for Environment and Agriculture. The library is publicly accessible and allows users to listen to, download, and visualize individual sound clips. Beyond supporting research, VLIZ hopes this library will bring underwater sound closer to the general public and raise awareness about noise pollution at sea.
Explore the Sound Library for the Belgian part of the North Sea: marinesoundlib.org
