"Part of the problem is in the brain," said Robert D. Frisina, assistant director of the International Center for Hearing and Speech Research, based at Rochester Institute of Technology's National Technical Institute for the Deaf.

Although a hearing loss may be more noticeable in seniors, changes in the brain that promote hearing loss may occur in middle age with a decline in feedback or speech recognition, Frisina said.

Their most recent findings were the subject of a presentation last month during an international meeting in New Orleans for the Association of Research in Otolaryngology.

Researchers at the University of Rochester are using that data while testing the hearing of mice. Scientists know certain medical conditions, such as Type II diabetes, can cause diminished hearing over the years. They hope to know whether the hearing is restored when the mice recover from the diabetes.

Another discovery is that too much or too little calcium impedes communication between nerve cells and their release of chemicals, called transmitters, that allow signals to be understood.

And in some cases, age-related hearing loss is inherited maternally. Those more at risk should take steps to protect their hearing at a younger age, Frisina said.

Nearly 1,000 subjects have had their hearing tested since the study, funded by a $6.3 million National Institute of Health grant, began in 1991. The study will last until at least 2008.

Sitting in one of three soundproof booths, volunteer subject Jean Susser, 75, of Ontario, Wayne County, wore a pair of headphones Thursday and had a series of hearing tests. She learned of the test through friends and thought it would be a good excuse to have her hearing tested.

"I'm a little hard of hearing," Susser said.

In one test, she was asked to type on a computer what words she was listening to. If she was correct, the next word would be softer; if she was wrong, the next word would be louder.

Next Susser was asked to differentiate between sounds she heard through the headphones, whether they were a constant "chhh" sound or one that was broken, such as "chhh-chhh."

"It was difficult at first. You have to pay attention," Susser said. "Once I paid attention, it went easier. And knowing this might help someone makes me feel better."

By Greg Livadas