The ringing noise in their ears is probably the last thing on the minds of combat soldiers. But many audiologists suggest it's affecting more and more soldiers, and it's time to sit up and take notice.

Tinnitus, an annoying and sometimes painful ringing in the ears, is a common result of exposure to loud noises such as bombs and gunfire, according to Jennifer DuPriest, director of advocacy and public policy for the American Tinnitus Association.

With more soldiers claiming disability for tinnitus each year, DuPriest warns that unless more is done to prevent hearing damage in the field, the number of troops in pain will continue to rise - along with the cost of post-deployment care.

"In 2006, the government paid out $539 million in disability for tinnitus alone," DuPriest said. "If you couple that dollar amount with what was paid out for hearing loss disability, the total is well over $1 billion for fiscal year 2006 alone."

Since 2000, the number of veterans claiming disability for tinnitus has gone up 18.2 percent per year, DuPriest said. It rose 20 percent between 2004 and 2005, which marked the largest jump since tinnitus became compensable in 1945, she said.

DuPriest said the cost of compensation has hit record highs and will continue to rise unless something is done to better protect troops' hearing.

"If nothing changes and the rates stay the same, we'll be paying out $1.1 billion by 2011," when nearly 1 million veterans will have tinnitis, DuPriest said. "And that's only in compensation. That doesn't even include research."

Maj. Richard Oberman of the New Hampshire National Guard said one reason payments are up is that the Army strongly encourages soldiers who show hearing damage to file a claim.

"We've done a better job educating people about the benefits they're entitled to," Oberman said. "We advise them to go to the VA Center and file. We tell them, 'You're eligible for this, and it's OK to claim it.'"

In all, about 50 million Americans suffer from tinnitus, DuPriest said, and about 12 million have it chronically. Between 1 million and 2 million Americans are completely debilitated, experiencing depression and anxiety, she said.

Even though there is no cure for tinnitus - and little treatment - DuPriest said there are still things the military can do to help prevent further damage. She said a proper tinnitus test should be the first priority.

"The standard hearing test does not pick up tinnitus since it's a noise generating in the auditory cortex in the brain," DuPriest said. "People with tinnitus hear a noise because there's some kind of disconnect going on in the brain, so it's overcompensating. It's called a phantom pain, like when a soldier loses a leg but says he can still feel pain in his toes."