Underwater noise impact of offshore wind farms during construction and operation phases

Abstract

The two potentially noisier phases of an offshore wind farm are construction and operation. During the construction phase, high noise levels are radiated to the environment, both in air and water, due to engineering works such as pile driving. In the operation phase, the acoustic power radiated by each wind turbine is much lesser, but their usual life-span is 20-25 years. The aim of this paper is to describe a normal mode propagation model designed to predict the underwater noise impact afforded for an offshore wind farm in both phases. The model needs as inputs the acoustic data of the underwater sources (power level and spectrum), the oceanographic data of the medium (sound velocity and density in water and sediments, wind speed, depth, acoustic spreading law in the area) and the coordinates of the wind turbines. As a result, the model provides both the 2D overall noise map around the farm or the overall noise level along a line, as compared to the background noise.