Reducing underwater noise when installing subsea structures

Offshore wind farms have the potential for large impacts on clean energy generation, as wind speeds are higher at sea than on land. However, this benefit comes at a high cost for marine life, which can suffer greatly during the installation of offshore wind foundations.

Junfei Li, from Purdue University, is presenting work on mitigating noise pollution during monopile offshore wind farm installation on Tuesday, May 20, at 1:00 p.m. CT as part of the joint 188th Meeting of the Acoustical Society of America and 25th International Congress on Acoustics, running May 18–23.

“To build offshore wind farms, monopile foundations are commonly driven into the seabed with hydraulic impact hammers, generating strong noises that propagate 50 kilometers or more from the installation site, potentially inducing auditory injury and behavioral change in marine species,” said Li.

These deep foundations are crucial for physically supporting wind farms—and other structures—above the sea. Most current mitigation techniques are limited by high energy demands or challenges with transportation and deployment.

Li and his colleagues instead developed a metamaterial comprising of carefully arranged plates that trap air within and act as guides for the sound. With their metamaterial in place, sound from monopile installation can be reduced by 40 decibels, an improvement over the 25-decibel reduction of other methods. The material is modular and foldable, making its transport and deployment easy and inexpensive.

Li said the sounds created during these processes have wide-reaching impacts.

“The high-intensity, impulsive noise generated by pile driving has the potential to affect a range of wildlife—including marine and freshwater fish, sea turtles, and marine mammals,” said Li. “It may lead to a range of behavioral changes in marine mammals and may lead to auditory or physical injury in some species of fish.”

The researchers hope to scale up their technology for deployment in future offshore wind farm constructions, as well as for monopiles used in bridge construction and oil drilling platforms.

“Human-generated underwater noise is a critical—yet often hidden—environmental stressor. It’s not just background sound; it actively harms marine life, affecting their ability to survive and thrive,” said Li. “We must acknowledge the severity of our acoustic impact on the underwater world and work toward reducing it.”