大衛提議創造一道「氣泡簾幕」（air bubble curtain），以及發送警告信號，讓海豚在工程開始之前有時間離開該區。
Pile driving and industrial noise can adversely impact dolphin behavior, communication, and breeding as the noise is detectable up to 40 kilometers (25 miles) from the source, new research reveals. Bottlenose dolphins that live in designated Special Areas of Conservation throughout the United Kingdom, including Dorset, Anglesey and Cornwall, were found to be at significant risk from pile driving noise.
Long used to place docks, bulkheads and bridges, and more recently to site off-shore oil platforms, pile drivers now are being used ever more frequently as countries place wind turbines in off-shore waters to generate electricity with strong coastal winds.
Dolphins use echolocation to find food and locate predators. They send out high frequency vocalizations that bounce off surrounding objects and fish, giving the dolphins a detailed picture of their surroundings.
At 9 kHz, pile driving noise is capable of masking strong vocalizations within 10–15 kilometers and weak vocalizations up to 40 kilometers, J.A. David, a member of the Chartered Institution of Water and Environmental Management, documents in a scientific paper published in the latest issue of "Water and Environment Journal". The impacts of masking are expected to be limited by the intermittent nature of pile driver noise, the dolphin's directional hearing, their ability to adjust vocalization amplitude and frequency, and the structured content of their signals.
Operations should be restricted to low tide and suspended during calving season, David advises. An exclusion zone should be monitored before any activity starts, and marine work should cease if a dolphin enters the work area. David calls for further research into the reactions of marine mammals to industrial noise to help mitigate future effects in relation to the increase in off-shore industry, such as the construction of wind farms.
He proposes creating an air bubble curtain and issuing a ramped warning signal to give dolphins time to leave the area before work commences.
The sound blocking capabilities of an underwater air bubble curtain were tested in 2000 by scientists with the Marine Mammal Research Program at Texas A&M University. A team led by Texas A&M Professor of Marine Biology Bernd Würsig found that underwater bubbles can inhibit sound transmission through water due to density mismatch and concomitant reflection and absorption of sound waves.
Because the bubble curtain effectively lowered sound levels within kilometer of the activity, the experiment and its application during construction represented a success, Wursig said, suggesting that this measure should be considered for other areas with high industrial noises and resident or migrating sound-sensitive animals.