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Unexpected noise discovered at deepest part of world's ocean

After sending equipment more than 36,000 feet below the ocean's surface, scientists heard something they didn't expect: noise.

NOAA sent equipment 7 miles down the Challenger Deep trough in the Mariana Trench, near Micronesia, over the summer and came away with new observations.

"You would think that the deepest part of the ocean would be one of the quietest places on Earth," Robert Dziak, NOAA research oceanographer and chief project scientist, said. "Yet there is almost constant noise."

The equipment picked up on sounds from earthquakes, whales, ship propellers and "the clamor" of a typhoon that barreled overhead during the three-week project, Dziak said.

Scientists sent a hydrophone down the trough, which is deep enough to fit Mt. Everest.

The ceramic hydrophone had to be lowered with extreme caution, dropping only 5 meters per second due to rapid pressure change.

Atmospheric pressure at the bottom of the trench is more than 16,000 pounds per square inch (PSI), according to NOAA. At the average home or office, the PSI is 14.7.

Originally dropped in July, the hydrophone sat in the depths of the ocean for three months. Scientists were unable to safely recover the hardware sooner due to an active typhoon season and the mission ship's schedule.

Officials are expecting to launch similar project in 2017, this time sending a deep-ocean camera with the hydrophone.