Those ubiquitous white buds that are barely visible in the ears of most iPod users ship as standard equipment with every iPod purchase. Garstecki, chairman of Northwestern's Communication Sciences and Disorders Department, said his warning is similar to those issued in the 1980s when Walkmans and portable compact disc players were all the rage with music listeners.

"We're seeing the kind of hearing loss in younger people typically found in aging adults," Garstecki said. "Unfortunately, the earbuds preferred by music listeners are even more likely to cause hearing loss than the muff-type earphones that were associated with older devices."

Small and Loud

Earbuds pose several kinds of problems, according to Garstecki and other audiologists. First, the earbuds' close proximity to the eardrum, in combination with their ability to magnify the sound signal by as much as six to nine decibels, raises the intensity of the sound from one similar to the noise output of a vacuum cleaner to that of a motorcycle engine.

Technological advances that have extended the playing time of music-listening devices, as well as their capacity to store and play back a broad spectrum of music, encourage users to listen to music for longer periods of time than did older portable players, Garstecki explained. All of this increases the likelihood of hearing loss, he said.

"I have an audiologist friend at Wichita State University who actually pulls off earphones of students he sees and, in the interest of science, asks if he can measure the output of the signal going into their heads," Garstecki said. "He found that often students were listening at 110 to 120 decibels."

According to Garstecki, that decibel level is on par with the noise level found at rock concerts and can lead to hearing loss after only one hour and 15 minutes of exposure.

The Golden Rule

Garstecki and other audiologists want music listeners to adopt their so-called "60 percent, 60 minute" rule. The solution, they said, is to spend no more than one hour each day listening to an MP3 player or iPod with the volume level lower than 60 percent of the maximum.

"If music listeners are willing to turn the volume down further still and use different headphones, they can increase the amount of time that they can safely listen," Garstecki pointed out.

Earbud users can avoid permanent hearing loss in the middle ranges, the range necessary to hear a conversation in a noisy environment -- such as a restaurant, for instance -- by replacing them with safer, old-school style headphones that are larger and rest over the entire ear. Or they can try using noise-canceling headphones that Garstecki fears won't be a likely choice because of their cost and ungainly appearance in contrast to the inexpensive, diminutive earbuds.

"Unlike earbuds, noise-canceling headphones quiet or eliminate background noise, Garstecki explained. "That means listeners don't feel the need to crank up the volume so high as to damage their hearing."