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Researchers recently discovered that whales can adjust their hearing in response to sound levels. (Doug Perrine / Nature Picture Library)

How Whales Keep the Noise Down

Scientists think some whales "plug their ears" to block ocean noise

By Laura Leigh Davidson | null null , null

You might think of the sea as a calm, quiet place to live. But boat motors, underwater oil and gas drilling, and other human activities cause all kinds of loud noise. The U.S. Navy estimates that 250,000 sea mammals each year suffer from hearing loss and even deafness just from the loud booms emitted by the Navy’s underwater listening devices.

But scientists recently discovered that whales have developed a way of protecting themselves from hearing loss. Somehow, the whales desensitize their hearing to the underwater uproar.

“It’s equivalent to plugging your ears when a jet flies over,” Paul E. Nachtigall, the University of Hawaii marine biologist who led the discovery team, told The New York Times. “It’s like a volume control.”

Noise pollution is very hard on whales and other sea mammals that use their sensitive hearing to navigate the waters, to care for themselves and their young, to keep track of other sea dwellers, and to find a mate. So researchers are looking for ways to help these ocean mammals keep their hearing healthy.

Although scientists haven’t quite determined how whales operate their “volume control,” the early findings have made them hopeful they can develop an auditory warning signal that will help whales and other sea mammals clear out of a particular area before a supernoisy event takes place.

At a facility in Oahu, Hawaii, Nachtigall and his team are studying how toothed whales and dolphins hear. Dolphins and whales use echoes to help them navigate, a process called echolocation. Using special equipment, the researchers were able to see the brain waves that are connected to the mammals’ hearing. They found that the mammals could adjust their hearing in response to their own echolocation. This discovery made the scientists wonder if the mammals could adjust their hearing to human-made sounds.

Their key test subject was a false killer whale named Kina. First, researchers played a soft, mild warning tone for Kina. They followed this sound with a harsh, loud tone. After a while, the scientists could see in Kina’s brain waves that when she heard the soft signal tone, she began desensitizing her hearing to prepare for the big sonic boom she knew was coming.

“It shows promise as a way to mitigate the effects of loud sounds,” Nachtigall told The Times. “People are generally very excited about it.”

Although researchers will continue their work to find a way to help protect the hearing of sea mammals, experts say the best protection is a reduction in the amount of undersea noise.

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