MOREHEAD CITY - Critics and supporters sounded off Tuesday on the Navy's contention that sonar training off the North Carolina coast does not pose a significant threat to animals or human activities.

A public hearing in Morehead City drew about 60 people who listened to Navy plans to continue sonar training with surface ships, submarines and aircraft in offshore areas as it has for decades. Two officials of the Navy League, a civilian organization that supports the service, said the Navy needs the training to detect hostile submarines.

Bud Strong of New Bern said the league has confidence in Navy environmental studies.

But representatives of environmental groups expressed concern about the Navy's review of environmental issues and letters of opposition.

Michelle Nowlin of the Southern Environmental Law Center in Chapel Hill said her group is concerned about the cumulative harm to the ocean and marine life from Navy activities. She said the Navy had concluded that an absence of information about harm to marine animals indicated there was no harm. "This is not the case," she said.

The hearing focused on a draft environmental impact statement for using mid- and high-frequency sonar technology near existing operating areas along the East Coast and Gulf of Mexico. One alternative examined areas that could be used year-round; another identified those that could be used on a seasonal basis; and a third deals with areas of "increased awareness" where sonar training would not be allowed.

But the Navy prefers a no-action alternative that would allow existing training. "What you guys have experienced for the past 40 years is what we want to continue doing," Jim Brantley, a spokesman for the Navy in Norfolk, Va., said in an interview.

There would be no major harm to sea turtles and marine mammals such as whales and dolphins, the study said, but sonar training could affect the behavior of animals.

Keith Jenkins, a marine scientist who worked with the Navy on the study, said it might cause the animals to stop feeding or move out of an area. In some cases, he said, the sound might keep them from hearing normal sounds around them.

The Navy has to obtain a permit from the federal government because the activities are considered harassment of protected species.

According to the Navy study, sonar is essential because of the worldwide proliferation of modern, quiet diesel submarines.

Sonar technology involves bouncing sound waves off underwater objects to determine what they are. Brantley said the training is needed so technicians can learn how to identify whether an object is an animal, an obstruction or a vessel.

"That's why we need to train the way we fight," he said.

He said the Atlantic fleet training is different from the Navy's proposal for an undersea warfare training range. The Navy has identified waters by Onslow Bay, near the Camp Lejeune Marine Corps base, as its preferred location for a 661-square-mile sonar-training range.

The range, 65 miles offshore, would be used to train crews on ships, submarines and aircraft carriers to use sonar to detect and battle submarines.

"The two projects are totally separate," Brantley said.