The National Oceanic and Atmospheric Administration dropped a titanium-encased hydrophone into the bottom of the Mariana Trench (where the Challenger Deep is located) to record ambient noise, and the results were stunning. Everything from typhoons to boat propellers are still audible at this depth. 

Mother Nature added a bit of its own music to the mix. In these short clips you’ll hear the hauntingly beautiful calls of a baleen whale and a toothed whale or dolphin:

Another revealed the rumblings of a 5-magnitude earthquake:

But what’s even more astonishing is the unnatural noise still audible at these incredible depths. Challenger Deep lies near Guam, a regional hub for container shipping with China and the Philippines, so the hydrophone also picked up sounds from boats passing 36,000 feet overhead:

NOAA’s Office of Ocean Exploration and Research funded the hydrophone project in the hope of establishing a baseline for ambient noise in the deepest part of the Pacific Ocean. Once researchers establish that baseline, it can be used to determine if human-created noise increases over time—a potential issue for whales, dolphins and other aquatic animals that use sound to communicate.

To learn more about NOAA’s other exciting ocean exploration projects, click here!