In addition to earlier findings of a specific type of timing problem that limits our hearing as we age, the group is now finding increasing evidence of a feedback problem in the brain that diminishes our ability to hear.
"Traditionally, scientists studying hearing problems started looking at the ear," says Robert D. Frisina, Ph.D., professor of Otolaryngology at the University of Rochester Medical Center and an adjunct professor at Rochester Institute of Technology. "But we are finding patients with normal ears who still have trouble understanding a conversation."
Oftentimes it's this ability of the brain, not hearing itself, that is diminished in older people who say they don't "hear" well. The loss is detected most markedly in tests that measure a person's ability to hear a sentence amid a background of babble. The recently discovered feedback problem is central to this problem, says Frisina.
"The number-one hearing complaint among the elderly is that they have trouble hearing speech because of background noise. Someone might hear fine in a quiet environment like their home, but when they go to a restaurant or a meeting or a party, it sounds like chaos to them," Frisina says. "That's partly because the feedback system is failing."
Six years ago the same team of researchers reported finding a closely related brain timing problem where people are not as adept as they once were at detecting slight gaps in speech. While the average person can hear sound gaps of about 2 milliseconds apart, someone with a timing problem may be anywhere from 2 to 50 times worse detecting such gaps, which are crucial - though unconscious - for properly hearing consonants and vowels.
While most people gradually lose the ability to hear high frequencies as they age, the feedback and timing problems account for many of their complaints about hearing, Frisina says.
MEDICA.de; Source: University of Rochester Medical Center