Not a single word on turbine foundations? Construction of offshore wind turbines often involves ramming steel foundations into the ground with a set of pulses that are really loud [1]:

> A hydraulic or diesel fuelled hammer hits the pile repeatedly to drive it into the seabed. The single acoustic pulse created during impact is between 50 and 100 ms in duration with app. 30 - 60 beats per minute. It usually takes several hours to drive one pile into the bottom. This activity creates high levels of sound pressure and acoustic particle motion that are transferred through the pile into the water and seabed. Noise is radiated from the pile itself, but it could also radiate back from the seabed into the water column. The sound from pile driving is transient and discontinuous, to be compared with the more broadband and continuous sound from an operational wind farm. Several acoustic measurements of sound pressure during piling have been performed, showing source levels of over 180 dB re 1μPa(peak) at 1 m (Madsen et al., 2006; Betke et al., 2004; Betke, 2008; Erbe, 2009).

So 180 dB re 1μPa. While this is well below air guns or sonar (around 240 db for the air guns) [2], this is definitely comparable to the noise created by tankers (around 180 dB as well) [3].

[1]: https://www.diva-portal.org/smash/get/diva2:391860/FULLTEXT0... [2]: https://www.arc.id.au/SoundLevels.html [3]: http://cetus.ucsd.edu/Publications/Publications/PAPERS/McKen...