Many people look to the ocean when they’re looking to relax and get a little peace and quiet. As soothing as the sea can be, you’d think it would only become calmer the further down you submerged into the depths – you’d be wrong.

Audio recordings obtained over 23 straight days in Challenger Deep – the Mariana Trench’s deepest part at 36,000 feet below the surface – captured noise, a lot of noise. We know almost nothing about the place or what life is like in its depths.

Here’s the sound of a boat 6.7 miles overhead  as it passes by:

“Light does not propagate underwater very far,” oceanographer Bob Dziak of the National Oceanic and Atmospheric Administration told Gizmodo. “But sound waves travel long distances through the Earth’s oceans. Acoustics is really the best way to get a good picture of deep ocean environments.”

Dziak is actually the one who led the effort to record audio from Challenger Deep. The process wasn’t easy since it was uncovered territory. It required his team to design equipment that could take 16,000 pounds of pressure per-square-inch that while their equipment was 7 miles deep. All that was required next was a device to slowly lower a hydrophone to acclimate to the pressure on its way down and patience over the course of a three week recording session.

A magnitude 5 earthquake near Guam on July 16:

A baleen whale call before and after the quake:

Once the recordings were retrieved, they discovered Challenger Deep was host to a wide range of noises. From ships to whale calls and even noises from the Earth itself, the results were the opposite of what anyone expected.

“I was surprised by just how cleanly we can record whales, ships, and all sorts of activity taking place at the surface,” Dziak noted. “It is akin to sending a deep-space probe to the outer solar system. We’re sending out a deep-ocean probe to the unknown reaches of inner space.”

More whale calls:

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