The unknown noise of wind power will be investigated

20 February, 2024

Underwater noise from planned large wind turbines risks affecting both wildlife and Sweden’s defense capabilities.

Now researchers will find out how such wind farms will sound below the surface.

Lillgrund wind farm south of the Öresund Bridge. There are now plans for larger wind turbines and researchers are to investigate how much underwater noise they can cause. Archive image. Photo: Johan Nilsson / TT

Offshore wind power is planned to be greatly expanded, but how the new wind farms will coexist with both people and animals is a hot question.

There are many questions about the noise levels they generate underwater.

Today’s offshore wind turbines cause noise disturbances to the environment during the construction phase. The piling can be heard many kilometers away and the sound scares away fish, among other things.

When they are in operation, the noise can have an effect locally in the park and cause stress, among other things, but according to the available research, they do not cause direct harm to fish and other marine life.

Vibrations and sounds

That’s what Mathias Andersson, marine biologist and research leader at the Total Defense Research Institute (FOI), says.

But the wind turbines now being planned are on a much larger scale. The foundations can have a diameter of up to 15 meters compared to a maximum of 8 meters today. How these larger wind turbines will sound is the big question, he says.

He leads a project that was recently awarded five million Swedish kroner by the Swedish Environmental Protection Agency to provide answers.

The researchers will measure underwater noise and vibrations in the water and seabed from the Kriegers Flak wind farm south of Trelleborg. Using models, they will then calculate the noise from larger wind turbines.

Alien underwater craft

The knowledge must be able to be used in the environmental testing of offshore wind power and eventually lead to limit values for sound-sensitive marine animals.

Increased background noise below the surface can also affect military defence systems that use sonar to track alien underwater vehicles.

The idea is for the Swedish Armed Forces to gain knowledge of the operational noise level at an early stage during the environmental assessment process, in order to be able to analyze the consequences of wind power for the defense capability themselves, says Mathias Andersson.

The project is carried out by researchers at FOI and KTH in collaboration with Vattenfall.

The researchers will use hydrophone systems to measure underwater noise from the wind turbines. Photo: FOI

Underwater sound is very important for many marine animals’ perception of their surroundings and their communication.

Seals and porpoises have inner ears that resemble those of humans. The inner ears of fish differ and perceive vibrations. But species with a swim bladder, such as cod, can also perceive sound pressure in the same way as mammals. For example, male codfish use sound to attract females, and aquarium experiments show that underwater noise makes it harder for the fish to find each other.

Invertebrate animals such as clams, worms, and snails – which form an important base in ecosystems – perceive sound via vibrations, like fish. There is still very little knowledge about how they are affected by underwater noise.

Source: Mathias Andersson

Text: Hanna Odelfors/TT
Photo: Johan Nilsson/TT, FOI/Press

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