Today's ubiquitous（普遍存在的） MP3 players permit users to listen to crystal-clear tunes at high volume for hours on end（连续地） -- a marked improvement on the days of the Walkman. But according to Tel Aviv University research, these advances have also turned personal listening devices into a serious health hazard, with teenagers as the most at-risk group. One in four teens is in danger of early hearing loss as a direct result of these listening habits, says Prof. Chava Muchnik of TAU's Department of Communication Disorders in the Stanley Steyer School of Health Professions at the Sackler Faculty of Medicine and the Sheba Medical Center. With her colleagues Dr. Ricky Kaplan-Neeman, Dr. Noam Amir, and Ester Shabtai, Prof. Muchnik studied teens' music listening habits and took acoustic measurements of preferred listening levels.

The results, published in the International Journal of Audiology, demonstrate clearly that teens have harmful music-listening habits when it comes to iPods and other MP3 devices. "In 10 or 20 years it will be too late to realize that an entire generation of young people is suffering from hearing problems much earlier than expected from natural aging," says Prof. Muchnik.

Hearing loss before middle age

Hearing loss caused by continuous exposure to loud noise is a slow and progressive process. People may not notice the harm they are causing until years of accumulated damage begin to take hold（抓住，扛着） , warns Prof. Muchnik. Those who are misusing MP3 players today might find that their hearing begins to deteriorate as early as their 30's and 40's -- much earlier than past generations.

The first stage of the study included 289 participants aged 13 to 17. They were asked to answer questions about their habits on personal listening devices (PLDs) -- specifically, their preferred listening levels and the duration of their listening. In the second stage, measurements of these listening levels were performed on 74 teens in both quiet and noisy environments. The measured volume levels were used to calculate the potential risk to hearing according to damage risk criteria laid out by industrial health and safety regulations.

The study's findings are worrisome（令人烦恼的） , says Prof. Muchnik. Eighty percent of teens use their PLDs regularly, with 21 percent listening from one to four hours daily, and eight percent listening more than four hours consecutively. Taken together with the acoustic measurement results, the data indicate that a quarter of the participants are at severe risk for hearing loss.