Abstract
When giant steel piles of up to 40 metres in length are rammed into the seabed at one-second intervals, the noise can be heard over 50 kilometres away. When offshore wind turbines are being erected the noise of the ramming can damage the hearing of marine mammals. The Little Bubble Curtain noise reduction method was the focus of the eponymous RAVE project. This project investigated the effectiveness of millions of air bubbles rising up around the pile in order to reduce the effects of the ramming noise. Before the ramming began, the marine mammals were first scared off with high-frequency acoustic signals to get them out of the construction area. The concept of a bubble curtain, which requires flotation bodies all around the pile and the use of divers, was a great technical and organisational challenge. It emerged that the sea current easily causes the bubbles to drift away, which can consequently reduce overall efficiency.