Fidelity

I've never been obsessed about the sound quality of CDs versus MP3s. And while I can "hear" the difference in warmth between vinyl and CDs, the latter never bothered me to the least. I almost never go to live performances. So am I trading away a fuller enjoyment of music for convenience without realizing it?

MP3s have won the war of the formats because of technology, not because of their audio quality. "It's like hearing through a screen door," says neuroscientist Daniel Levitin of McGill University, author of "This Is Your Brain on Music."

But what is the price of inferior audio quality? Can poor audio touch the heart as deeply as better sound? John Meyer, who designs and builds some of the world's best speakers at his Meyer Sound Labs in Berkeley, Calif., doesn't think so.

"It turns you into an observer," Meyer says. "It forces the brain to work harder to solve it all the time. Any compression system is based on the idea you can throw data away, and that's proved tricky because we don't know how the brain works."

It could be that MP3s actually reach the receptors in our brains in entirely different ways than analog phonograph records. The difference could be as fundamental as which brain hemisphere the music engages.

"Poorer-fidelity music stimulates the brain in different ways," says Dr. Robert Sweetow, head of the University of California-San Francisco audiology department. "With different neurons, perhaps lesser neurons, stimulated, there are fewer cortical neurons connected back to the limbic system, where the emotions are stored."