While the Sea of Cortez, where the study took place, is relatively quiet, other waters, such as the Mediterranean sea, are polluted with the din of commercial vessels, ferries, and jet skis.
"In many places the oceans are filled with a generalized acoustic smog," said Clark. "Commercial shipping lanes around major ports are as noisy as the tarmac at Kennedy Airport."
But like people chatting in a crowded room, whales must have the ability to pick out signals from the rest of the noise, said Payne. The ocean is a very noisy place with the chatter of animals, the wind and storms, the grinding of the tides, and constant earthquakes.
Sonar initially generated concern when 16 rare and elusive beaked whales beached themselves in the Bahamas after the Navy used a mid-range sonar in March 2000. There is still no conclusive evidence whether the Navy's new low frequency sonar will cause problems for fin or blue whales.
"The frequency of the sonar is four octaves above the those used for fin whale communication, but we don't know whether it will be bothersome to the fin whales or other marine life," said Payne. The same is true for increases in commercial traffic. "We are faced with real genuine ignorance."
One study published in Nature in 2000 showed that low-frequency active sonar altered the singing behavior of humpback whales. Humpback songs were associated with reproduction but it is not clear whether the alterations would affect reproduction rates or were needed to compensate for the noise.
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