Whales rely on their own form of sonar to communicate, and larger species, including blue and gray whales, use frequencies similar to the special sonar. The only discernible effect was that whales swam around the sonar source, said Joe Johnson, a program manager with the Navy's Submarine Warfare Division. But environmentalists say some types of sonar can cause ear hemorrhages that disorient whales, leading to beachings. Most who spoke at yesterday's meeting cited the Bahamas beaching and one that occurred in Greece after a 1996 NATO naval exercise as proof that all sonar is dangerous to marine mammals. But we just don't know enough about the long-term impact of this system.
Scientists say there is no direct evidence linking the Bahamas sonar use to the beaching.
But scientifically, it is still a hypothesis. However, the Navy tested low-frequency active sonar effects on whales to levels of only 155 decibels even though the Navy has deemed sounds as loud as 180 decibels to be safe for marine life. If any come closer than a kilometer from the ship, where decibel levels are higher than 180, it will be turned off, Johnson said.