The sea monster goes ‘bloop’—or does it?

Could the source of a mysterious "bloop" sound be an unknown sea creature? Image: MARK GARLICK/SCIENCE PHOTO LIBRARY / Getty Images Get the Popular Science daily newsletter💡 Breakthroughs, discoveries, and DIY tips sent six days a week. Terms of Service and Privacy Policy. In 1997, the U.S. National Oceanic and Atmospheric Administration (NOAA) detected an unusual noise in the remote south Pacific. This in itself was not remarkable. NOAA’s undersea microphones or “hydrophones,” primarily used for monitoring geological activity, often pick up sounds whose origin is not immediately apparent. NOAA researchers give these sounds nicknames, including Upsweep, Sea Train, and Julia (named because it sounded like a woman’s muffled voice ). But this particular noise was like nothing scientists had heard before. Extremely low in frequency, it was also extremely loud, picked up by sensors over 3,000 miles apart . The mystery sound rose and fell over the course of one minute. When sped up 16 times to make it audible to human ears, it sounded like “bloop.” This became the noise’s nickname as scientists puzzled over what could have produced it. What was special about the Bloop? Due to its rapid changes in frequency, the Bloop bore some resemblance to marine animal sounds. However, it was much, much louder than a blue whale, the loudest-known animal. The call of a blue whale can be heard about 1,000 miles from its source. While impressive, this is less than a third of the distance that the Bloop traveled. “We’re suspecting that it’s ice off the coast of Antarctica, in which case it’s darn loud,” NOAA oceanographer Chris Fox said of the Bloop in 2001 . Though the Bloop was louder than the sounds typically associated with shifting ice, it was so much louder than any known animal that NOAA considered crumbling polar ice floes to be the most plausible explanation. Baleen Whale Vocalizations: What Do Whales Sound Like? The blue whale, a kind of baleen whale, is considered the loudest animal on the planet. Video: Baleen Whale Vocalizations: What Do Whales Sound Like, NewportWhales The blue whale, a kind of baleen whale, is considered the loudest animal on the planet. Video: Baleen Whale Vocalizations: What Do Whales Sound Like, NewportWhales However, in a separate interview Fox gave for New Scientist in 2002 , he acknowledged that the Bloop had similarities to animal sounds. This led New Scientist writer David Wolman to speculate, “Is it even remotely possible that some creature bigger than any whale is lurking in the ocean depths? Or, perhaps more likely, something that is much more efficient at making sound?” Was the Bloop a sea monster? Other media outlets soon took this remote possibility and ran with it. “One theory is that [the Bloop] is a deep sea monster , possibly a many-tentacled giant squid,” CNN reported in 2002. (While the giant squid is very real , it is not known to be capable of making noise). The mystery of the Bloop became a tantalizing symbol of how