Noise polluters include chattering shrimp, commercial shipping and screeching icebergs in polar waters. Human activity at sea has undoubtedly generated additional noise and the best place to avoid noisy underwater neighbours is in the South Pacific, far from any shipping lanes. We need to know whether the diffusion of sound can affect mating or even migration . Ocean researchers are deliberately setting off controlled underwater explosions in a clever technique designed to monitor global warming .
Sound travels faster in warm water than in cold water.
The travel time of a sound signal from a source near California to a receiver near Alaska, for example, will decrease if the intervening ocean warms up, and will increase if the ocean cools down . Previous experiments have shown the feasibility of measuring ocean temperature by transmitting signals between sources and receivers separated by up to 2,000 km. But the group has been attacked by some environmentalists who have been calling for more intensive monitoring of marine life or even a complete halt to the experiments. The attacks intensified after three dead humpback whales were discovered near one ATOC sound source off the coast of California in 1996. During offshore exploration, powerful underwater air guns are deployed from seismic survey vessels .