No one should be surprised by the recent whale stranding in Hawaii ["Whales' Plight Revives Sonar Theory," front-page, July 11], thought to be the result of active sonar testing by the Navy in the area. We've been warning for years that such deployment could doom countless species of marine life.
Since February 1998, the Animal Welfare Institute has tracked the correlation between Navy tests and whale deaths. Each time strandings occur, the government says, "We didn't do it."
We believe that active sonar kills whales by either causing hemorrhaging (in the brain and tissues near the ear bones) or startling them into a rapid rise that results in gas bubbles in the blood ("the bends").
Although strandings alert us to a problem, whales tend to sink when they die. Researcher Robin Baird estimates that only about 5 percent of gray whales that die while traveling the highly populated California coast are found. So, we don't know how many whales and other marine creatures are killed or harmed by the Navy's use of active sonar.
The Navy has set 145 decibels as the maximum safe level for humans in water. The Animal Welfare Institute proposes that this level be the maximum level of ocean sound pollution permitted globally, with the caveat that this level still may be too high in many areas.
Animal Welfare Institute
Whales may be upset or panicked by sonar, but we have no conclusive evidence that sonar directly physically harms them. Decibel scales used for sound in water and in air are not directly comparable because acoustic properties differ in water and air.
When whales beach themselves after sonar exposure, it is apparently because they are fleeing the sonar (which may resemble the prey-locating sonar of predator killer whales), and the beach gets in the way.
As someone knowledgeable about acoustics, I can recommend a simple solution for the Navy -- be sure that any whales fleeing the sonar have open ocean ahead of them. But don't deprive sailors of necessary training.
The writer is a professor of physics at Washington University.