Underwater sound produced by operational floating wind turbines

Deployment of offshore wind turbines is growing rapidly. Conventional "fixed bottom" wind turbines are limited to water depths of ~60 m, so deployment of offshore turbines to greater water depths requires floating systems. Both fixed bottom and floating turbines produce operational noise that impacts the marine environment. While the operational noises from fixed bottom turbines are relatively well understood, floating turbines are comparatively novel technologies and there is uncertainty as to the noise they will produce and its impact on the marine environment. Results from acoustic surveys of two floating wind farms off the Scottish Coast are presented; Kincardine wind farm which uses semi-submersible floating systems; and Hywind which uses a floating spar structure. The acoustic signature of each consists of continuous tonal noise related to drivetrain vibration and transient broadband events related to the mooring systems. A machine learning algorithm was used to discriminate between drivetrain noise and mooring noise. Sound propagation modelling was used to determine the source levels for turbines at each wind farm allowing a comparison of the noise signature of different floating structures.