Long Range Acoustic Device (LRAD)
Last year, the Japanese whaling vessels surprised the Sea Shepherd by installing some military-class LRADs (Long Range Acoustic Devices).
Basically it works by concentrating a beam of sound (similar to the high-pitched shrill of a smoke alarm) about 33 inches in diameter on a target. At a meter away, it can produce a sound of 146db -- loud enough for massive pain and permanent ear damage. More plausible is that the Sea Shepherd will experience sound of roughly 90db at 1,000 feet -- resulting in disorientation and headaches. (For reference, a smoke detector is around 100db)
To battle this device, it's expected that crews will equip earplugs or headsets to diminish the noise. It's also interesting to note that a flat surface could be utilized to re-direct sound back to the originator -- giving the Japanese a taste of their own weaponry.