Eugene Weekly : News : 7.19.07

iPod to iDeaf
Will headphones cause hearing loss?

The recent popularity of MP3 players has led to possibilities for continual noise exposure previously unknown to the human ear. But noise-related hearing damage is still preventable, according to an Oregon Health & Science University hearing researcher.

Billy Martin, professor of otolaryngology and head and neck surgery at OHSU, spoke of iPod risks to a crowd of at least 50 at Luna during a July 12 Science Pub presentation entitled “iPod Madness: Will the iPod Generation Soon Be Deaf?”

The title was a bit of a trick question. iPods get a lot of attention because they are a successful, well-marketed product — as of April 2007, 100 million of them had been sold worldwide — but the bigger question, Martin said, is whether noise in general is dangerous.

This requires understanding the anatomy of the human ear. What we understand as sound is actually vibration. When sound vibrations travel into the ear canal, they pass through the eardrum and then follow the tiniest bones in the human body to the cochlea, which encode the vibrations into electrical messages to be processed by the brain. The cochlea in each ear are lined with 18,000 tiny hair cells, the whole lot of which can fit on the head of a single pin. Hearing loss occurs when these hair cells are damaged, often by loud noise.

“They weren’t designed for rock concerts,” Martin said. “They were designed to hear a twig snap before a lion ate you in the jungle.”

Once damaged, these hair cells cannot regenerate themselves, Martin said. Birds have the capability to regenerate damaged hair cells, and research is currently being done on mice to try to replicate that regeneration in mammals, but until then, humans must take care of their hearing by regulating the loudness of the noise they are exposed to and how long they are exposed to that noise.

At 100 percent output, most MP3 players register 103 decibels — a volume that is only safe for five minutes. While members of the Baby Boom generation damaged their hearing at rock concerts blaring more than 120 decibels, at least they eventually went home from the concerts. Even users of personal cassette players a couple of decades back had to take frequent breaks to flip tapes over, and battery life was limited, Martin said. In contrast, MP3 players can dispense music uninterrupted for up to 15 hours, and Martin knows of middle school students who go to sleep listening to their iPods.

So will iPods make you deaf? True, Deaf Life magazine has ads for iPods, as Martin displayed ironically during his presentation, but this should not be taken as cause for alarm. (A Google search into the matter clarifies that some people who are deaf and hearing impaired find uses for iPods — one example, as reported by Deaf Today, is that the gallery VSA Arts of Colorado uses video-capable iPods to provide American Sign Language interpretations of their art exhibits.)

Rather, MP3 players can be used without causing hearing damage by following these two rules, Martin said: the 80/90 rule, which means listening to a MP3 player at 80 percent volume for no more than 90 minutes, and the arm’s length rule, which means that a person listening to an MP3 player should be able to carry on a conversation with another person an arm’s length away without removing an earphone.

More good news is that one can listen to an MP3 player at up to 60 percent of its maximum volume without time constraints, and that newer versions of the iTunes software include a mechanism to limit the maximum volume of one’s iPod. Another issue is that people tend to crank the volume on their MP3 players dangerously high when excessive background noise is present, but insert-style or noise canceling earphones can help block out background noise.

For more information on preventing noise-related hearing damage, Martin recommended an educational website he helped produce,

Martin’s presentation was part of the Science Pub series, which is sponsored by the Oregon Museum of Science and Industry (OMSI), the UO’s College of Arts and Sciences, The Science Factory and Luna, 30 E. Broadway. These interactive presentations take place at 7 pm (come earlier to order food and drinks) on the second Thursday of every month. Next month’s presentation on Aug. 9 will be OSU professor Sam Chan discussing invasive plant species.

Eugene’s Science Pub topics for the fall will likely include string theory, planetariums and the wave laboratory at OSU, said Amanda Thomas, coordinator of adult learning programs for OMSI.

Science Pubs began in Portland and continue to draw 110 to 150 people per month there. Thomas said the goal of OMSI’s adult education programs is to make science relevant to people and get them to include it in their busy lives.