BACKGROUND: As portable digital music players -- iPods and other MP3 players -- become more and more popular, people are becoming concerned about whether they are dangerous to our hearing. Now hearing researchers have measured specific sound levels in a variety of players using several different types of earphones. They used this information to develop the first detailed guidelines with safe volume levels for listening to the iPod with earphones. They also evaluated the output levels of several other popular players to determine any risks to hearing from using these devices.
ABOUT HEARING LOSS: Loud sounds stress and could damage the delicate hair cells in the inner ear that convert mechanical vibrations in the air (sound) into the electrical signals that the brain interprets as sound. If exposed to loud noises for a long time, the hair cells can become permanently damaged and no longer work, producing hearing loss. Noise-induced hearing loss can be caused by two types of noise: sudden bursts, such as firearms or fireworks; or continuous exposure to loud noise, such as motorized recreational vehicles, loud sporting events, power tools, farming equipment, or amplified music. For a person to lose their hearing because of continuous exposure, it would depend on how loud the sound was and how often and for how long they heard it. It takes repeated exposures over many years to cause a noise-induced hearing loss in both children and adults.
WHAT THEY FOUND: The researchers conducted a study observing the listening habits of 100 graduate students listening to iPods through earphones. They found that all the players had very similar sound output levels. Also, in-ear earphones, which broadcast sound directly into the ears, are no more dangerous than headphones placed over the ears. However, if the user listens to music in noisy surroundings, they are much more likely to raise the volume to risky levels, suggesting that people should seek quieter listening areas when possible, and use earphones that block out background noise.
RECOMMENDED LEVELS: The more often and the louder you player your player, the more likely you'll experience some hearing loss. To come up with recommended listening times and sound levels, the researchers compared the players' volume levels to the minimum sound level for the risk of hearing damage: 85 dBA. Typically, a person can tolerate about two hours of 91 dBA per day before risking hearing loss. The researchers recommend listening to iPods for -- hours a day with earphones if the volume is at 80% of maximum levels. Listening at full volume is not recommended for more than 5 minutes per day using the earphones that come with the player.
The Acoustical Society of America contributed to the information contained in the TV portion of this report.
ON THE WEB: http://www.hearingconservation.org http://www.dangerousdecibels.org http://www.newswise.com/articles/view/524384