What does the deepest part of the ocean sound like?

Researchers from the National Oceanic and Atmospheric Association, Oregon State University and the U.S. Coast Guard dropped a "titanium-encased hydrophone" into the waters of the Challenger Deep trough of the Mariana Trench near Micronesia, and lowered the device seven miles deep. For 23 days, the device recorded sounds, and when the researchers pulled it up to have a listen, they were surprised by how loud it was.

“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. “Yet there is almost constant noise. 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.”

In early 2017, researchers plan to lower another recording device, this time equipped with a video camera to explore the same trough to help them understand and predict the conditions of Earth’s environment.