It seems every time you turn around life is getting louder. Car radios, construction noise, jets, those guys on television talk shows. Everything in the modern world is loud, loud, loud.

Recent studies show that exposure to loud noises hurts more than your ears--it can even hurt your heart.

Here's the general idea: when the ears hear a really loud sound they can trigger a hormone called norepinepherine to go into the blood. The norepinepherine causes the heart to absorb more calcium. The extra calcium, in turn, can damage cell membranes.

Why is that bad? Damaged cells release what are known as free radicals. You may have heard of these in other news stories--free radicals are molecules that have unbound electrons, which makes them react strongly with other molecules. When uncontrolled, these reactions aren't always good: free radicals, for example, can damage DNA.

To see whether plain old noise causes free-radical damage in the heart, a group of Italian researchers at the University of Pisa exposed ten rats to one hundred decibels of white noise. Before you imagine an atomic blast, though, a hundred decibels is about what you encounter in a loud dance bar. A second group of rats lived in peace and quiet. When their hearts were compared, sure enough, the rats that experienced the noise had more damaged membranes.

Does the same thing happen in humans? It's possible, though scientists are still working to figure out whether the noise itself is the issue or simply the general stress it produces. Of course, if overall stress is hurting the heart, people have even more problems than rats do.