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It's a noisy world. Some cope by listening to their MP3 players; others go a step further and try to drown out the world's noise by listening to their MP3 players at high volume levels. Some younger adults, in particular, crave the rock concert sound experience, the high intensity assault on their hearing. At first, this may leave them with a temporary hearing loss and/or tinnitus; as time passes, they can suffer permanent damage. MP3 players, including iPods, are capable of recreating the high intensity sound experience of a rock concert...sometimes for listening enjoyment; other times, to mask environmental noise, i.e., commuter train, crowd. One design decision potentially exacerbates the risk of damage from the usage I have described-that being a loosely fitting earpiece or earbud. Earbuds allow sounds in the environment to leak in, often causing the user to turn up the volume. Another design feature with mixed benefit is the capacity these devices have for storing literally hours of music. The combination of high signal intensity level and long listening duration is a proven formula for permanent, irreversible hearing loss! Unfortunately, currently, manufacturers have yet to publish studies or information about the safe usage of these devices.
Still, there are safety steps consumers can take like limiting use to 60% volume for approximately one hour daily. If higher volumes are desired, the time spent listening should be decreased...if lower volume settings are used, that time could be increased. Another guideline is if the iPod user cannot hear others talk, they have the volume set too high. The same is true if others can hear what the iPod user is playing. And, one might consider using noise-canceling or older, muff-type earphones instead of earbuds which in themselves may increase signal intensity by as much as 9 dB.
Obviously, the impact of MP3 players and the iPod in particular on hearing has worldwide interest and relevance. Print and broadcast media have reported on the issue in the United States, Canada, South America, Europe, Asia, and Australia. At Northwestern University, in addition to press inquiries, we've also been contacted by hearing scientists, parents, young children, teenagers, engineers, research labs, high school science teachers, retired pilots, noise pollution control activists, and others.
Yet, consumers want to know how to use these devices safely-where to set the volume control and how long they can listen without harming their hearing. Generally, they want to know the intensity level of the signal/music when the device is 'just on,' at mid-volume setting, and at 'full on' and how that information relates to how long they might be able to use their device without causing permanent damage to their hearing; in essence, they want an earpiece that blocks out unwanted sound, minimizing the need to turn up the volume. Consumers apparently would not only welcome, but may soon also demand that manufacturers make modifications to better ensure safety for their hearing.
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