Rain falling on the surface of the ocean can be heard a mile deep

and at some frequecies it's louder than passing ships, according to oceanopgraher Jeff Nystuen. Nystuen, of Applied Physics Laboratory at the U of Wash, is one among scientists studying how sound travels through the ocean to better understand how loud, manmade noises might affect marine creatures. Loud underwater noises, particularly US Navy sonar, have long been blamed by environmentalists for the fatal beachings of whales. The Natural Resources Defense Council and other plaintiffs alleged in a federal lawsuit last fall that the Navy's mid-frequency sonar used for detecting enemy submarines disturbs and somtimes kills whales and dolphins. The Navy settled a similar lawsuit 3 years ago by agreeing to limit it's peacetime use of experimental low-frequency sonar.