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Silent buoy

August 7, 2009

Hydrophones on mooring lines could detect whale sounds but frequently it is too noisy. The problem was that in often violent seas, surface buoys moved up and down, pulling the lines so that the sound of water whooshing past the hydrophones overwhelmed all other sounds. To solve the problem, WHOI engineers designed a two-tiered mooring line, separated by a steel flotation sphere. In rough seas (right panel), the tough, stretchable “Gumby hose” on top acts like a bungee cord, absorbing the pulls of the surface buoy. The bottom line is decoupled from the movements of the top line; it remains a stable, quiet platform for the hydrophone.

(Illustration by E. Paul Oberlander, Woods Hole Oceanographic Institution)