The National Oceanic and Atmospheric Administration, Oregon State University, and the U.S. Coast Guard sent a titanium-encased hydrophone down to the deepest part of the Mariana Trench, known as the Challenger Deep, about seven miles below the surface. You might expect such a deep, dark underwater environment to be blissfully quiet. You would be wrong. The resulting audio from NOAA’s hydrophone is hauntingly noisy. Below, you can listen to the sounds from a toothed whale or dolphin, a baleen whale, and an earthquake that happened near Guam.
In order to capture these sounds, the researchers had to be very careful about how they sent the ceramic hydrophone to its murky destination. With such pressure threatening to damage the instruments, the hydrophone was lowered slower than five meters per second. At the bottom of the Mariana Trench, the atmospheric pressure is more than 16,000 PSI. The recorder was sent out in July 2015 and gathered sound for 23 days, then retrieved. The researchers are planning another audio gathering expedition for 2017, but this time the hydrophone will record longer, and will have a camera to capture images of the creatures creating these terrifying noises.