However, a problem has arisen from increased use of personal music devices (PMDs). A growing number of people are suffering from hearing loss suspected to be caused by using "ear bud" headphones at an increased volume level.

There is no direct evidence linking using ear buds and PMDs to sensorineural hearing loss at this time. Plenty of studies are being conducted, though, to see just what the effects of such usage are. Researchers are suspect that they will be able to link ear buds and PMDs to increased rates of hearing loss in younger patients because of the way the human ear itself is structured.

Sensorineural hearing loss occurs when tiny hairs in the cochlea are damaged. Damage to these hairs results in decreasing ability to pick up sound vibrations from the environment and translate them into nerve impulses that we register as sounds. It tends to occur gradually in both ears over time; it is an effect of living, but it may be minimized by limiting exposure to loud, high-pitched and high frequency noises.

With PMDs, we are able to listen to music for longer periods of time and at louder volumes. It is volume that is key. Many PMDs use ear buds to deliver sound. Earbuds, inserted inside the ear, are very close to the eardrum. These earpieces have a clear digital output that is virtually distortion free even at very high volumes. The volume is unable to escape the ear canal because the earbud acts as its own earplug-it disallows sound escape. Comparatively, foam headsets can be played at louder volumes and will register as less powerful signals because much of the volume escapes through the foam and into the surrounding environment.

According to audiologist Douglas L. Beck, three factors are involved in hearing loss with ear buds. They include personal susceptibility, the volume at which the media is listened to, and for how long it is listened to at that volume. "You can listen forever at reasonable loudness. If it's too loud, it doesn't matter how long. It's a matter of loudness. If you can hear headphones two or three feet away, it's probably too loud."

The point is this: While there is no direct evidence yet directly linking ear bud used for extended time at high volumes, there probably will be in a few years. It is better to prevent hearing damage before it becomes permanent hearing loss. Doctors recommend a five-minute rest from a PMD for every hour it is used. Try to reduce the volume of your PMD, or use foam headphones.

Source: http://www.tnhonline.com/media/paper674/news/2005/10/21/Commentary/Health.Column.Turn.Down.Those.Ipods-1028841.shtml