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Hydrophone being lowered into the Challenger Deep trough in the Mariana Trench in 2015. Credit: National Oceanic and Atmospheric Administration
If you really want to get away from it all, you might try the Challenger Deep — the deepest point in all the world’s oceans. This trench in the western Pacific Ocean bottoms out at about seven miles — deep enough to drop in Mount Everest with more than a mile to spare.
Even this dark, remote world isn’t completely quiet, though. In fact, some recent research found that it’s quite noisy. From the call of a whale...to the whine of the propellers of a passing ship...to the rumble of a nearby earthquake...it’s never really silent.
Researchers dropped an underwater microphone — a hydrophone — into the Challenger Deep in July of 2015. It was specially designed to withstand the pressure of the trench — 16,000 pounds per square inch — more than a thousand times the air pressure at the surface.
The hydrophone was attached to a battery and a recorder, which captured more than three weeks worth of sounds. Researchers retrieved it in November, and analyzed the recordings. They heard abundant marine life, ships, and even a typhoon roaring overhead.
Researchers plan to record even more sounds in the Challenger Deep in 2017. Ship traffic, underwater exploration, and other human-caused sounds present a risk to whales and some other forms of marine life, which are particularly sensitive to sound. So keeping an “ear” on the oceans can help researchers monitor how life is adapting to the ever-louder ocean depths.
