Mitigating Underwater Noise from Shipping, Seismic Airgun Surveys, and Pile Driving Using Best Available Technology and Environmental Practices

Best Available Techniques/Technology (BAT) and Best Environmental Practice (BEP) are required under several international agreements. For shipping noise, this generally includes minimizing cavitation by optimizing the propeller design to the hull and to usual operating conditions, and better maintenance, which often also improve efficiency. Slow steaming, or reducing ship speed, has the advantage that no retrofitting is required, and greenhouse gas emissions are reduced. Quieter seismic airgun alternatives, such as Marine Vibroseis, a controlled sound source that can be tailor-made to the specific environmental conditions, can reduce the unnecessary mid- or high-frequency energy and sharp rise time of airguns. Mitigation measures for airgun surveys should show proof of efficacy, avoid sensitive areas and times, and not proceed in conditions of poor visibility such as at night. Quieting technologies would almost certainly require fewer mitigation measures. Especially many new quieting technologies and alternative low-noise foundations have been developed for pile driving, mainly due to governments like Germany setting noise limits. Application of quieting technologies that reduce sound at source will likely be the most effective way to reduce the environmental impacts of underwater noise, and quieting methods that also reduce greenhouse gas emissions or encourage technological innovation should be especially encouraged.