If a screaming infant on an airplane, road rage-filled motorist with an unusual love for their car horn, or annoying neighbors who refuse to turn down the bass have ever driven you to dream about the quietest place on Earth, we have some relevant news for you: It’s not the bottom of the ocean.
In July of 2015, the National Oceanic and Atmospheric Administration (NOAA), in conjunction with Oregon State University and the U.S. Coast Guard, spent three weeks continuously monitoring ambient noise from the bottom of the Mariana Trench—the deepest point in the ocean which, at a depth of 7 miles, could hold all of Mount Everest with 7,166 feet (2,183 meters) to spare.
The intent of the project was to establish a baseline for ambient noise in the area, as scientists are uncertain how the increasing volume of human-created noise—which has risen steadily in recent decades—might affect marine animals that use sound to communicate, navigate, and feed, like whales, dolphins, and certain fish.
Recording at the bottom of the sea
Of course, getting recordings at 36,000 feet under the sea was no mean feat.
The hydrophone used to capture the sound. (Credit: NOAA)
“The pressure at that depth is incredible,” said Haru Matsumoto, an Oregon State ocean engineer who aided in the research, in a statement. “We had to drop the hydrophone mooring down through the water column at no more than five meters per second to be sure the hydrophone, which is
made of ceramic, would survive the rapid pressure change.”
In fact, the pressure at the bottom of the Mariana Trench is more than 16,000 pounds per square inch (PSI)—the average home or office is less than 15.
After the hydrophone was deployed from the Guam-based U.S. Coast Guard Cutter Sequoia in July, ships’ schedules and typhoons prevented the researchers from recovering the flash drive with all its data. However, it remained anchored to the ocean floor until they were finally able to return in November.
The results were pretty surprising.
“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.”
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Image credit: NOAA
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