Acoustic model for monitoring marine noise
Researchers refined and tested an underwater sound propagation model, which could be used to protect marine mammals from construction noise.
Peter Dahl, University of Washington, Applied Physics Laboratory and Department of Mechanical Engineering
Per Reinhall, University of Washington, Department of Mechanical Engineering
The researchers refined a new noise-propagation model they developed using measurements taken at various distances and depths during recent construction in Puget Sound. This model accounts for bathymetry and seabed sediment composition, which can affect sound propagation. They incorporated sediment maps of Puget Sound into the model and applied it to similar shallow water sites on the East Coast.
Underwater noise from marine construction can threaten marine mammals such as killer whales and other sensitive species. Developers must establish monitoring plans to protect animals from harmful noise levels. Current monitoring plans are based on a simple model for underwater sound transmission that may not accurately estimate levels within tens of square kilometers. Use of this simple model can add significantly to a construction project’s cost and timeline without improving protection for marine mammals and other species.
Initial results showed that the shape of the zone of elevated noise levels can change with the seasons. They demonstrated good agreement between the model and actual underwater noise measurements, in contrast to predictions based on the traditional model. The Washington State Department of Transportation waited to adapt its underwater construction protocols to the new model until it was fully tested.