Page 15: of Marine Technology Magazine (April 2016)

These waves, known as surface-gravity waves, do not travel nearly as fast, far, or deep as acoustic-gravity waves, yet under the right conditions, they can gen- erate the powerful, fast-moving, and low-frequency sound waves. minutes. Researchers at MIT have now identi? ed a less dra- this energy and travels much faster and deeper.

matic though far more pervasive source of acoustic-gravity This interaction may occur anywhere in the ocean, in par- waves: surface ocean waves, such as those that can be seen ticular in regions where surface-gravity waves interact as from a beach or the deck of a boat. These waves, known as they re? ect from continental shelf breaks, where the deep-sea surface-gravity waves, do not travel nearly as fast, far, or deep suddenly faces a much shallower shoreline. Usama Kadri, a as acoustic-gravity waves, yet under the right conditions, they visiting assistant professor and a research af? liate in MIT’s can generate the powerful, fast-moving, and low-frequency Department of Mathematics, says the team’s results establish sound waves. The researchers have developed a general theory a concrete and detailed relationship between surface-gravity that connects gravity waves and acoustic waves. They found waves and acoustic-gravity waves, which, until now, scien- that when two surface-gravity waves, heading toward each tists had suspected did not exist. Understanding this relation- other, are oscillating at a similar but not identical frequency, ship, he says, allows researchers to describe how energy is their interaction can release up to 95 percent of their initial exchanged between gravity and acoustic waves. He says this energy in the form of an acoustic wave, which in turn carries energy could be vital for many marine life forms, and it could www.marinetechnologynews.com

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