Underwater Noise of Two Operational Tidal Stream Turbines: A Comparison

This study measured underwater noise of two 1.5 MW tidal stream turbines (Atlantis AR1500 and Andritz AHH1500) at the MeyGen project site, Pentland Firth, Scotland, UK. Underwater turbine noise may be important for acoustically sensitive marine mammals to detect turbines and avoid collision, but it may also negatively affect them, as well as fish and invertebrates (e.g., injury, disturbance, and habitat exclusion). The turbines’ source levels were determined, and a 3D-noise model predicted the acoustic footprints of the existing and future turbine arrays. Highest noise levels were between 50 and 1000 Hz for both turbines. However, noise levels (25 Hz–25 kHz) recorded from the Andritz turbine were generally lower in amplitude compared to those recorded from the Atlantis turbine. The results show that harbor seals (and probably other marine mammal species) will be able to detect operating tidal turbines at distances that are likely sufficient to avoid collision. The MeyGen project aims to build out to 400 MW in later stages of the project which will increase the predicted noise footprint ranges presented here, with unknown environmental consequences. This highlights the importance of including these results on underwater noise in strategic marine spatial planning of larger tidal turbine arrays.