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Oregon Scientists Eavesdrop On Ocean's Deepest Deep, Surprised How Noisy It Is


Have you ever wondered about life in the deepest depths of the ocean? Oregon-based oceanographers did, so they dropped a microphone seven miles down. What they heard came as a surprise.

National Oceanic and Atmospheric Administration and Oregon State University scientists and engineers based in Newport, Oregon, and Seattle get credit for the first deployment of a microphone and recorder encased in titanium to the deepest place in the world’s oceans — the Challenger Deep in the Mariana Trench southeast of Guam.

“It was an engineering feat,” said Robert Dziak, a NOAA research oceanographer and the chief project scientist. “You would think that the deepest part of the ocean would be one of the quietest places on Earth. Yet there is almost constant noise.”

The hydrophone recorded for three weeks last summer before its flash drive filled up. The instrument was not recovered until months later though due to persistent typhoons and other demands on the Guam-based U.S. Coast Guard cutter the project team used to get on location.

Then all the different sounds in the audio file they downloaded took a while to analyze and identify. The recording contained the rumblings of numerous nearby and distant earthquakes. The scientists picked out the high pitched calls and low pitched vocalizations of several different whale species. The churning waves of a typhoon could also be heard at one point, as well as the thrum from the propellers of many passing ships.

“I was surprised how clear and loud the sounds were,” Dziak said. “Even though the whales are a few hundred feet probably from the sea surface and the ships are at the sea surface, the sounds seven miles deep are as clear as they can be.”

NOAA explained it funded the recording mission to establish a baseline for ambient noise in the deepest part of the ocean. Lots of additional research is happening along the West Coast to study possible impacts on whales and other marine creatures from increasing human-caused underwater noise.

“There aren’t that many measurements out in the world’s oceans of what noise is going on now and how it may be changing in the future,” Dziak said in an interview with public radio Wednesday. “There is clear recognition that noise is an issue in the ocean to marine ecosystems and marine animals that use sound to orient, navigate and to find food.”

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