Loud Sound May Pose More Harm Than We Thought

Matt Garlock has trouble making out what his friends say in loud bars, but when he got a hearing test, the result was normal.

Recent research may have found an explanation for problems like his, something called “hidden hearing loss.”

Scientists have been finding evidence that loud noise - from rock concerts, leaf blowers, power tools and the like - damages our hearing in a previously unsuspected way. It may not be immediately noticeable, and it does not show up in standard hearing tests.

But over time, Harvard researcher M. Charles Liberman says, it can rob our ability to understand conversation in a noisy setting. It may also help explain why people have more trouble doing that as they age. And it may lead to persistent ringing in the ears.

The bottom line: “Noise is more dangerous than we thought.”

His work has been done almost exclusively in animals. Nobody knows how much it explains hearing loss in people or how widespread it may be in the population. But he and others are already working on potential treatments.

To understand Liberman’s research, it helps to know just how we hear. When sound enters our ears, it’s picked up by so-called hair cells. They convert sound waves to signals that are carried by nerves to the brain. People can lose hair cells for a number of reasons - from loud noise or some drugs, or simple aging - and our hearing degrades as those sensors are lost. That loss is what is picked up by a standard test called an audiogram that measures how soft a noise we can hear in a quiet environment.

Liberman’s work suggests that there’s another kind of damage that doesn’t kill off hair cells, but which leads to experiences like Garlock’s.

A 29-year-old systems engineer who lives near Boston, Garlock is a veteran of rock concerts.