Hard to hear in crowds? Blame your brain

Published 10:05 pm Monday, December 29, 2008

NEW YORK — Wonder how younger people can understand conversation in a crowded room when everything sounds like mush to you? Part of the problem may be your brain.

In fact, it may lie in your brain’s dimmer switch for controlling the input from your ears. That bit of brain circuitry appears to falter with age, and scientists are getting some clues about why.

If you have trouble hearing in a noisy room, you’re experiencing what’s sometimes called the cocktail party problem.

That can be one of the first signs of an age-related hearing loss — a more general problem that can creep in during middle age, and affects one-third of adults ages 65 to 75.

Scientists have long known that the brain not only receives signals from the ears, but can also talk back to them. And when there’s too much noise, this dimmer-switch brain circuitry tells the ears to reduce their flow of signals to the brain.

This helps the sensitive auditory system handle loud sounds that otherwise would overwhelm it and become distorted, as when a radio is turned up too loud for the speaker to handle.

In addition, since background noise at a party tends to be lower-pitched than speech sounds, the dimmer switch probably can block out that distracting noise more than it does the speech, said Robert ­Frisina of the University of Rochester in New York, who is studying the problem.

The brain has an added trick for focusing on a particular person’s speech rather than competing conversations, Frisina said. Since you’re probably facing the person you want to hear, his words arrive at both your ears at the same time and at the same volume. The brain can use that, along with the dimmer switch, to home in on that person’s speech, Frisina said.

Another crucial element lies within the inner ear, where sound is converted to nerve signals. That’s accomplished by cells that use delicate hairs to detect sound waves. These hair cells can be damaged by aging and by long hours in loud environments like rock concerts.

While scientists continue to study hearing problems, people who have trouble understanding their fellow partygoers can take some steps to help themselves. Anne Oyler of the American Speech-Language-Hearing Association suggests facing the speaker directly to get facial cues that might fill in some blanks.

And don’t be shy about admitting the problem and suggesting a move to a quieter place.