Some Parts Of ‘Silent World’ Sound Like Underwater Fiestas Screeching Icebergs Noted By Researchers

The “silent world,” as Jacques Cousteau called the ocean depths, is not so silent after all.

Some places in the deep blue sea are getting to be as noisy as Times Square at noon, researchers say.

Among the aquatic noisemakers: screeching icebergs in the Arctic Ocean, chattering shrimp along the South Carolina coast and clanging oil rigs in the North Sea.

While some places in the sea are as quiet as a Nebraska prairie at midnight, others sound like underwater fiestas, according to a study done by researchers at the New England Aquarium, the Massachusetts Institute of Technology and Cornell University.

Whaling areas in the North Atlantic have about the same noise level as a busy New York intersection, or more than 100 decibels, says Arthur Baggeroer, an ocean engineering professor at MIT.

The South Pacific registers the least amount of noise - about 65 decibels - because of its distance from commercial shipping lanes.

“Unlike things on the surface, sounds underwater can actually be louder because of a chamber effect,” Baggeroer says. “Black Sea dolphins in Russia can make sounds that we may not be able to hear, but they sound quite loud to other fish and animals.”

Baggeroer and fellow researcher William Spitzer say the ocean echoes as sounds travel through layers of water at different speeds, depending on temperature and water pressure. Sound travels faster at the surface and more quickly through warmer water.

“The result of that is sound that starts in the layer, bounces up against the top of that layer and it tends to get louder,” says Spitzer, an oceanographer for the New England Aquarium. “It’s like speaking in a tube.”

The sounds traveling through the sea include the gurgling of toad fish in the Caribbean; the bell-like call of walruses; the squeaking of dolphins; and the thumping of motors and other machinery.

The research was compiled from studies over the last decade, including data recently declassified by the Navy. The Navy for the past several years has used high-powered underwater microphones to monitor enemy submarines.

The research found that clicking noises of shrimp registered more than 80 decibels. Oil rigs can ring out about 180 decibels.

The key question now for researchers is how sound affects sea creatures, which detect noise and vibration through an auditory organ or a vein, called a lateral line, that runs across the body.

Other research has found that elephant seals in the North Pacific avoided shipping channels because of loud noises. And whales that died from oil rig explosions showed evidence of damage to their hearing organs.

“What we now need to find out is if low-frequency sounds made by man can hamper communication between animals,” Baggeroer says. “We need to know whether the diffusion of sound can affect mating or even migration.”

MEMO: This sidebar appeared with the story: What’s next The key question now for researchers is how sound affects sea creatures, which detect noise and vibration through an auditory organ or a vein, called a lateral line, that runs across the body.