This is Shep O'Neal with the VOA Special English HEALTH REPORT.

Electronic devices are changing the way people listen to music. But studies show the devices may be causing hearing loss in many people. Some experts say people may be playing them too loud and for too long.

Researchers from Zogby International did a study for the American Speech-Language-Hearing Association. It involved three hundred high school students and one thousand adults. They were asked about their use of portable music devices. Some of the most popular are Apple Computer's iPod, C.D. players and portable laptop computers.

Forty percent of students and adults said they set the sound levels, or volume, at high on their iPods. But students were two times more likely to play the music at a very loud volume. More than half of the students said they would probably not limit their listening time. And about a third said they were not likely to reduce the volume.

The study found that more than half of the students and less than forty percent of the adults had at least one kind of hearing loss. Some reported difficulty hearing parts of a discussion between two people. Others said they had to raise volume controls on a television or radio to hear it better. And, some experienced ringing in their ears or other noises.

Hearing experts say part of the problem is the listening equipment people are using. They say large earphones that cover the whole ear are probably safer than the smaller earbuds that come with most music players. Earbuds are thought to be less effective than earphones in blocking out foreign noises.

Hearing loss may not be apparent for years. But once it happens, it is permanent. About thirty million Americans have some hearing loss. One third of them lost their hearing as a result of loud noises.

Experts at the Mayo Clinic in Minnesota say any sound above ninety decibels for long periods may cause some hearing loss. But most portable music players can produce sounds up to one hundred twenty decibels.

The American Speech-Language-Hearing Association is working with manufacturers and government officials on setting rules for use of portable music devices. The group says the best way to protect your hearing is to reduce the volume, limit listening time and using earphones that block out foreign noises.

This VOA Special English Health Report was written by Cynthia Kirk. This is Shep O'Neal.