Using sound to save whales from extinction

Perfect tenors
It also helps that right whales are almost perfect tenors. Their mid-range voices don't get washed out by high-pitched fizzing of bubbles or the low-register shifting of ocean-floor sand.

A big question is whether right whales talk enough when they migrate south for microphones to detect them consistently, the key to making audio surveillance worthwhile.

"The jury is still out on that," Clark said. "Mothers and calves are notoriously quiet. The mother's not out there to advertise she's got a baby. She doesn't want to attract killer whales or other company."

Clark can already tell a big difference in how right whales behave up north compared to when they travel south in the winter.

At Cape Cod, they're awfully chatty — sometimes yielding 2,000 recordings in a single day. The whales spend their summers and fall between Cape Cod and the Bay of Fundy. In the winter, they travel south through the Gulf of Maine toward warmer waters.

With the Brunswick study, Clark's team will compare its whale recordings with sightings logged by the aerial survey teams. Meanwhile, Clark is developing mufflers for the underwater microphones to eliminate noise caused by waves and storms.

A second array of satellite-tracking buoys will be placed offshore of Boston in the spring.

Inside each buoy, sounds picked up by the microphones are analysed by computers programmed to pick out right whale calls from other noises, using patterns based on hundreds of thousands of samples of the whales' voices. Electronic identifications are transmitted in real time by satellites, though Clark said humans still doublecheck to make sure they're right whales.

Multiple microphones picking up the same whale can triangulate its position from about 100 meters to as close as 50 feet, Clark said. Location points could be posted on maps on the Internet and used to issue warnings.

"Spying on animals like that is always full of surprises and it's also relatively inexpensive," Clark said. "Their voices are designed to be heard, so we're taking advantage of that."

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