Click on the links below to hear some of the sounds of the deep courtesy, of NOAA.
The hydrophone also picked up sound from ship propellers. Challenger Deep is close to Guam, a regional hub for container shipping with China and the Philippines.
The project, funded by the NOAA’s Office of Ocean Exploration and Research, was designed to establish a baseline for ambient noise in the deepest part of the Pacific Ocean. Human-created noise has increased steadily in recent decades and getting these first recordings allows scientists in the future to determine if the noise levels are growing and how this might affect marine animals that use sound to communicate, navigate and feed, such as whales, dolphins and fish.
Getting these first recordings wasn’t easy in an underwater trough deep enough to hold Mount Everest. “The pressure at that depth is incredible,” said Haru Matsumoto, an Oregon State ocean engineer who worked with NOAA engineer Chris Meinig to adapt the hydrophone. “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.”
While atmospheric pressure in the average home or office is 14.7 pounds per square inch (PSI), it is more than 16,000 PSI at the bottom of the Mariana Trench. Researchers deployed the hydrophone from the Guam-based U.S. Coast Guard CutterSequoia in July 2015. The device recorded sound continuously over 23 days, completely filling the flash drive. However, scientists had to wait until November to retrieve the hydrophone due to ships’ schedules and persistent typhoons. The device remained anchored to the seafloor until scientists returned.
Another OSU co-investigator on the project, Joe Haxel, will lead a planned return to Challenger Deep in early 2017, where the researchers will deploy the hydrophone for a longer period of time and attach a deep-ocean camera.