Deepest part of the world’s ocean is incredibly noisy, scientists say

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Guam — Unlike deep space, the deep sea is not a silent oasis, according to newly released recordings.

Researchers shared audio clips of ambient noise that were captured at a depth of more than 36,000 feet, about 7 miles, in the Mariana Trench, near the U.S. territory of Guam, according to a statement by the National Oceanic and Atmospheric Administration (NOAA) earlier this week.

“You would think that the deepest part of the ocean would be one of the quietest places on Earth,” said Robert Dziak, a NOAA research oceanographer and chief project scientist.

But scientists from NOAA, Oregon State University, and the U.S. Coast Guard were surprised by all the noise captured by the microphone they lowered into the Challenger Deep, known as the deepest point in the world’s seabed, for three weeks.

The goal of this project, funded by NOAA’s Office of Ocean Exploration and Research, was to establish a baseline for ambient sound in the deepest parts of Earth’s oceans. It’s one way researchers can measure how manmade sound, which has been steadily increasing throughout the years, is affecting marine creatures — since dolphins, whales and some fish use sound to communicate and feed.

What researchers found wasn’t peace and quiet, but a constant cacophony of noise at the bottom of the ocean.

“The ambient sound field is dominated by the sound of earthquakes, both near and far, as well as distinct moans of baleen whales, and the clamor of a category 4 typhoon that just happened to pass overhead.”

With sounds of geological tremors and mammal moans, the phrase ambient noise may be an understatement. The microphone also picked up on man-made noises such as ship propellers, which makes sense since Guam is a regional shipping hub.

Scientists dropped the microphone into the trough in July 2015 and recorded sound continuously on the seafloor for 23 days straight, which was not an easy feat because of the sheer water pressure. On land, the atmospheric pressure is about 15 pounds per square inch, but the bottom of Mariana Trench is 16,000 PSI. The mic was encased in titanium to compensate for this.

Researchers plan to return in 2017 and do a longer recording, this time with a deep-ocean camera.

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