Researchers from the National Oceanic and Atmospheric Administration, Oregon State University, and the U.S. Coast Guard collaborated last year on a massive research project. They wanted to send an unmanned hydrophone down to the deepest known parts of the ocean and listen. At 36,000 feet (11 km), the titanium-encased hydrophone descended to the Challenger Deep, an area in the Mariana Trench near Micronesia. As you might expect, the pressure at that level is extreme--16,000 pounds per square inch (PSI). To put that in perspective, a typical home's pressure is 14.7 PSI, according to the NOAA.
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