Turn down your iPod: How can biotech help prevent hearing loss?

The widespread use of iPods (and other portable mp3 players) continues to raise concern amongst heath care professionals and parents about the hazards of excessive exposure to loud music. Recent studies show that listening to loud music through headphones can result in temporary hearing loss. While the verdict is still out about whether loud music through iPods can result in permanent hearing loss, studies show that between 10- 20% of teenagers are listening to music on their mp3 players at volumes known to be at high risk for permanent hearing damage. This debate will likely be resolved in decades to come when hearing loss can be studied in adults from the iPod-generation. Nevertheless, precautions must still be taken in the present to prevent hearing loss in the future.

Noise-induced hearing loss is caused by the loss of sound-sensitive cells in the cochlea, which relay auditory information to the brain, following exposure to loud noise. These cells, once damaged, are permanently lost resulting in irreversible hearing impairment.

So, what qualifies as “loud”? According to guidelines from the National Institute for Deafness and Other Communication Disorders sounds above 85 decibels (dB) can lead to noise-induced hearing loss. The sound output of many mp3 devices exceed this 85 dB threshold. For example, maximum volume output form an iPod can surpass 115 dB. While very few people listen to their mp3 players at the highest volume, exposure to moderately loud (85 dB) music for extended periods of time will cause permanent damage to the sensory cells in the ear. As a general rule, the louder the sound, the quicker hearing loss damage can occur.

The good news, however, is that music listened to at or below 75 dB, even over extended periods of time, rarely results in permanent hearing damage. Thus, devices that make iPod listeners more aware about the intensity of the sounds they are putting in their ears or, even better, prevent the listener from exposing themselves to harmfully loud music altogether, are necessary. Design and use of such devices will have a significant impact on future hearing loss. Some currently available technological solutions that attempt to do just that are discussed below.

The most simple and accessible option to proactively preserve your hearing is by utilizing the “volume limit” feature that appears on a number of mobile device. The limiter is built into the device and allows you to choose the maximum volume output of your player. This feature is not available on all portable mp3 players, but can be found on all Apple products (iPod, shuffle, & nano). The use and setting of the volume limit option is dependent on the listeners awareness of and motivation to use it.

The volume limiter, although a good start for hearing loss prevention, provides a somewhat false sense of security. First, volume controls on mp2 players vary widely and can only be trusted as an arbitrary indicator of volume level. Measuring dB sound pressure level from the headphone speaker is a more accurate way to assess music volume. Second, it turns out that headphone quality and construction greatly impact the dB output of the mp3 player. Thus, a more effective hearing loss prevention product should limit sound output directly from the headphones. This strategy has been targeted by a number of companies, particularly focusing on preserving hearing in children and teenagers. Earbuds and headphones created by KidzSafe and Earzone limit the decibel output of headphones to less than 85 dB, effectively eliminating the worry for noise-induced hearing loss. Alternatively, EarSaver makes a low-priced adapter that reduces the output of factory headphones by an average of 18 dB. Although marketed towards kids, these products can also be used by adults.

Noise-cancelling and sound-isolating headphones limit the need for excessive volume music listening by reducing the amount of external noise that reaches the listener’s ears. In fact, loud environmental noise (i.e., airplane engines, subway, traffic) is one of the most likely reasons why people crank up the volume on their iPods. Drowning out background noise by increasing headphone volume inadvertently puts the listener’s ears in harms way. Noise-cancelling headphones contain a microphone in the earbud that samples noise in the environment. The headphone then supplies an inverse audio signal that effectively cancels out the impact of the external noise. This technology, while fabulous at reducing the listening volume on iPods, can be spendy. Good quality noise-cancelling headphones will range from $100 - $400.

Unfortunately, the successful use of the aforementioned products falls squarely on the shoulders of the owners of iPods and mp3 players. It is clear that a greater outreach is need to educate young listeners about the potential harm of mp3 player volume on hearing. Likewise, the available options for hearing loss prevention need to be more visible. Placing more overt warnings on mp3 packaging, rather than tucked away in an instruction manual, would be a good start. Recent research suggests that exposure to intense, or even moderate levels of noise can result in inner ear damage years before the perception of hearing loss. Thus, negative consequence from iPod use will only be measurable a decade or two from now, when hearing aid demand and hearing related health care costs from the iPod generation skyrocket. At that time, it is likely that government mandated warnings won’t seem so extraordinary. In the future, we may also need to consider implementing safety standards that limit the maximum volume delivery on portable mp3 device, much like those found in Europe.

Until then, the challenge remains to increase the visibility and affordability of quality, easy-to-use hearing prevention devices for portable mp3 players. The consumers are waiting. The awareness about the ills of constant, loud headphone listening is increasing. Industry needs to capitalize on the millions of headphone wearing teenagers and students and create more volume-reducing products that are affordable and accessible. They need to tweak their marketing strategy to entice the millions of iPod listeners to want to use the volume-limiting application because of it’s ease, to make the listener want to purchase the noise-cancelling headphones because they are equal in price or cheaper than existing earbuds, and to ultimately make a difference in the movement to prevent noise-induced hearing loss.