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Reviewed by: Jennifer Amaral
Last Update: November 13th, 2020
At the 17th Ronald C. Baird Sea Grant Science Symposium Session #3: Sediment and Sound, Jennifer Amaral (Ph.D. student, URI Ocean Engineering and Lead Scientist & Engineer, Marine Acoustics, Inc.) explains what vibratory pile driving is and how it varies from impact pile driving.
Most sound generated from offshore wind farms occurs during the construction phase and during this phase the impact pile driving generates most of the high level sound. Impact pile driving is the operation of forcing a pile into sediment; and, is typically used to secure the foundations of offshore wind turbines to the seabed.
In impact pile driving, a hammer hits the top of a steel pile and that impact sends sound into the air, water and sediment. This produces a very high-level impulsive noise that can be detected many kilometers away from the construction site. The level of sound generated depends on parameters such as the type of the pile, the amount of energy that the hammer is putting out and the environmental properties of the site such as the seafloor sediment and area bathymetry.
Unlike with impact pile driving, vibratory pile driving is a method in which the pile is vibrated into the sediment rather than being hammered in. The type and classification of the sound that is generated with vibratory versus impact pile driving is different. The sound generated from vibratory pile driving is classified as more non-impulsive, continuous sound as opposed to the impulsive and sharp sounds produced from impact pile driving.
Amaral explains the differences between these two methods of pile driving and notes that seeking out different methods of installing piles is one way to explore the reduction of sound pressure that enters the water column when constructing offshore wind farms.
Watch this video that provides a visual interpretation of a new method of pile installation that aims to reduce sound levels radiated into the environment.