Credit: FLIP NICKLIN/FLPA

J. Acoust. Soc. Am. doi:10.1121/1.3040028 (2009)

Killer whales (Orcinus orca; pictured) are a boisterous bunch, keeping track of each other in the underwater gloom by calling. Many whales, such as those resident in Puget Sound, near Seattle, Washington, have to contend with a great deal of noise made by motorized boats.

Marla Holt of the Northwest Fisheries Science Center in Seattle and her colleagues measured the calls of Puget Sound whales with a series of omnidirectional hydrophones. The whales pumped up the amplitude by one decibel for every extra decibel of background noise. The authors speculate that the increased effort may cost more energy, and that the noise may stress the whales or even disrupt their communications.