Some experts believe the sonar blasts killed at least a dozen porpoises. The divers were videotaping just off Victoria, B.C. and captured the piercing noise underwater.

The sound surrounded diver Lisa Martin and partner Dean Doan on May 5. Every 25 to 30 seconds, it hit. And as hard as it is to listen to on the tape, imagine this: The sound heard on the videotape was filtered through a dense plastic underwater camera-housing.

Nothing filtered the sound hitting Martin and Doan's ears. "Very, very high and piercing," describes Doan. "It's very sharp to the ear."

Martin says she not only heard, but felt, the sound. "It was a physical sensation, feeling the tones, it felt like you were being poked in the eardrum right through."

Whale advocates believe it's the same sound that sent resident killer whales scrambling and led to the deaths of more than a dozen harbor porpoises. That sound came from the USS Shoup conducting sonar training miles out in the Strait of Juan de Fuca.

Whale researchers captured and recorded the sonar May 5 through underwater hydrophones. But that tape doesn't come close to showing how intense the sonar really is underwater. "It's like standing next to the coach at a practice and he's blowing his whistle in your ear," describes Doan, "it's like a high-pitched pierce."

Since the incident with the Shoup, the Navy has changed its entire procedure for sonar training. Now before any training exercise can begin, they must first get approval from the commander of the entire pacific fleet.

The Navy says it's not done any sonar testing here since then, but stressed two weeks ago how important that training is. "This kind of training, in an area that's similar to potential conflict zones saves lives in combat," explains Navy spokesman Lt. Bill Couch.

Divers Martin and Doan understand the need for training, but question the when and where. "There's no doubt in my mind that what we heard would have been very disturbing if not damaging to any animal that relies on sonar," adds Martin, "no doubt in my mind at all." They don't believe it should happen where both humans and marine life could be affected.

The Federal Government is currently investigating the porpoise deaths. Scientists there don't expect to have any answers on the cause of death for at least another month.