Dear Doctor Column, August 28, 2006
iPods and Hearing Loss
Question:
I love my iPod and use it all the time -- can it damage my hearing?
Answer:
Listening to your iPod -- or any of today's popular portable MP3 music players -- too loudly or for too long could permanently damage your hearing, according to the American Academy of Audiologists and iPod manufacturer Apple Computer Inc. Being at close range to a single extremely loud sound such as a shotgun blast (about 145-165 decibels dB) can cause permanent damage to your hearing, but so can constant exposure to the more moderate levels of noise produced by iPods and other music players. At peak volume, iPods can reach 110 to 120 dB, which approach the level of a live rock concert.
Hearing is a complex process. Tiny hair cells in your inner ear amplify vibrations from sound waves, converting them into signals your brain can interpret. Excessive sound pressure can damage these hair cells, causing them to lose their ability to transfer sound to the brain. The result is noise-induced hearing loss, which can distort hearing and cause difficulty understanding speech.
Up to a point, hair cells can recover. If you've ever been to a loud concert, you may have noticed ringing or a sensation of fullness in your ears or some hearing loss immediately after the show. This type of hearing damage is usually temporary and clears within a day or two. Constant exposure to loud sounds, however, can weaken and eventually kill hair cells, which causes permanent hearing loss. Noise-induced hearing loss is directly related to both the volume of the sound and the duration of exposure. The longer and louder you listen, the greater the potential for lasting damage.
Most research in noise-induced hearing loss has focused on sound exposure in the workplace, and the National Institute for Occupational Safety and Health (NIOSH) has set the safe limit for noise exposure at 85 dB for 8 hours a day. Each time the noise level increases by 3 dB, safe exposure time is cut in half, NIOSH says.
Most people can hear sounds as low as 0 dB, the level of rustling leaves. The sound of a whisper is about 20 dB, rainfall, close to 45 dB. Normal conversation takes place at about 60 dB; vacuum cleaners and big-city traffic generate about 85 dB; your hairdryer produces about 90 dB; the buzz in a busy bar on a Saturday night might reach about 95 dB; and jackhammers and ambulance sirens operate at about 120 dB. As noted, iPods can reach 120 dB, and even minimal exposure to sound at this level can permanently damage your hearing.
So how long can you listen without causing lasting hearing loss? NIOSH and the Centers for Disease Control and Prevention offer these guidelines for continuous decibel levels and permissible exposure times:
85 dB - 8 hours
88 dB -- 4 hours
91 dB -- 2 hours
94 dB -- 1 hour
97 dB -- 0 minutes
100 dB -- 15 minutes
103 dB -- 7.5 minutes
106 dB -- less than 4 minutes
109 dB -- less than 2 minutes
112 dB -- less than 1 minutes
115 dB -- about 30 seconds
To reduce the risk of hearing loss, many experts suggest keeping your iPod or other personal music player set at no more than 60% of the peak volume and listening for no longer than 60 minutes a day. You can probably listen safely for longer if you're willing to turn the sound down even lower.
Because modern devices have a long battery life and can hold thousands of songs, people tend to listen longer. In addition, there is little research available on the effect of earbuds on hearing loss. Some scientist suspect earbuds, the tiny headphones that rest directly in the ear and are standard accessories with most MP3 music players, may increase risk of hearing loss because they produce a more intense sound signal.
To help prevent hearing loss:
- Know which noises cross the threshold of 85 dB, where hearing damage occurs.
- Wear earplugs or other protective devices when engaged in activities that expose you to loud noises. Most drugstores carry earplugs and more sophisticated ear muffs are available in hardware and sporting goods stores.
- Invest in headphones that block ambient sound, which will reduce the need to turn up your music player's volume. Noise-cancelling headphones are more expensive, and typically cost between $50 and $200.
- Make sure your children protect their hearing. Long-term exposure to loud music for extended periods starting in childhood could result in significant hearing loss by the time your child reaches adolescence or adulthood.
Children, who may not appreciate the many problems hearing loss can cause later in life, are especially vulnerable to noise-induced hearing loss. iPod owners may want to download Apple's free software update that allows users to set maximum volume limits on the player. Using a combination code, this update lets users and parents set and lock in volume caps. The free download is available for the iPod nano and fifth-generation iPod.