Listening to iPods for as little as 5 minutes a day can cause hearing loss.

Researchers Brian Fligor and Cory Portnuff estimate that a typical person could safely listen to an iPod for 4.6 hours at 70 percent of full volume using the supplied earphones without greatly increasing the risk of hearing loss.

However, listening to an iPod at full volume for more than 5 minutes per day, they say, could increase the risk of hearing loss in a typical person. These guidelines apply in general to other music players, such as the Sandisk Sansa and the Creative Zen Micro, which they found to produce similar volume levels.

In a separate study, researchers found that only 6% of iPod users listening in quiet environments turned their iPods up to unsafe levels. When in noisy environments, though, a full 80% listened at dangerous levels. When they used an “in-the-ear” earphone designed to block out background noise, only 20 percent exceeded sound levels considered to be risky.