Scientists tune in to sounds of the sea

larger   View a map that shows the location of the submarine cable off the central California coast that is being used for the Sound in the Sea Project.

By Richard Stenger
CNN Science and Technology

(CNN) -- Landslides. Earthquakes. Big whales. The oceans can be extremely loud, especially when one tunes in to the watery depths with special listening devices.

Hoping to learn more about the health of marine wildlife, scientists this week placed a stethoscope of sorts off the coast of California.

"There are a lot of things making noise down there. Whales, dolphins and fish, the rumblings of the Earth," said Chris Fox, an oceanographer with the National Oceanic and Atmospheric Administration.

Along with other researchers, Fox sailed days ago on a 285-long scientific ship from San Francisco to near Monterey Bay, where they deployed a series of electronic ears deep below in an underwater canyon.

The hydrophone array is the first dedicated to strictly civilian purposes. Historically, hydrophones have been put into service by the Navy to eavesdrop on the noisy purrs and whines of engines on ships and submarines.

Biologists realized that the military devices would be well suited to track animals too. But the classified recordings were difficult or impossible to procure. Thus was born NOAA's Pioneer Seamount program.

Unidentified 'bloop'

"It was sort of a plowshare sort of thing," said Fox, who works for NOAA's Pacific Marine Environmental Laboratory.

"We're particularly interested in blue whales, the largest animals ever, which are highly endangered. We've determined that they have a migratory path up and down the Pacific Coast."

The data will help scientists follow the migration of blue whales off the West Coast, he said.

Marine biologists expect to hear other sounds bouncing around the watery depths, like landslides and earthquakes, sometimes thousands of miles away on the other side of the Pacific Ocean basin.

They expect to hear any number of mysterious sounds that often ping the ears of sonar device listeners, including an unidentified "bloop" that crops up from time to time.

"I think it may be related to ice calving. It always comes from the south. We're suspecting that it's ice off the coast of Antarctica, in which case it's darn loud," Fox said.