iPods & Hearing Loss

Apple Computer, faced with research, complaints, and litigation claiming that the iPod can cause hearing loss, issued a new software update on March 29 that limits the personal maximum volume level of the iPod Nano and iPod models with video-playback capabilities. The free download, available at www.apple.com/ipod/download, prevents the player from outputting its potentially damaging maximum volume of 115dB. Parents can also use the feature to set volume limits on their child's iPod, and lock settings with coded combinations.

Apple's action was impelled by far more than a lawsuit. According to a recent nationwide telephone poll, more than half of the high school students surveyed report at least one symptom of hearing loss. The results of the poll, scientifically conducted by Zogby International, were released on March 14 at a panel discussion of national lawmakers and hearing experts. Convened by the American Speech-Language-Hearing Association (ASHA)—the professional, scientific, and credentialing association for more than 123,000 member and affiliate audiologists, speech-language pathologists, and speech, language, and hearing scientists—the panel was held at the National Press Club in Washington, DC.

The poll looked at the usage habits of high school students and adults who use portable audio devices equipped with earphones, including the iPod, other MP3 players, portable DVD players, and cell phones. The poll also probed the public's views about potential hearing loss from such devices, and what people believed would be the most effective way to convey a hearing-loss prevention message to consumers.

The polling found that high school students are more likely than adults to say they have experienced three of the four symptoms of hearing loss: turning up the volume on their TV or radio (28% students vs 26% adults); saying "What?" or "Huh?" during normal conversation (29% students, 21% adults); and having tinnitus or ringing in the ears (17% students, 12% adults). Less than half of the students (49%) say they have experienced none of the symptoms, compared to 63% of adults who claim to be symptom-free.

The national telephone survey of 301 high school students has a margin of error of ±5.8%. The separate survey of 1000 adults has a margin of error of ±3.2%. Margins of error were higher in subgroups.

Though a telephone poll can neither test for hearing loss nor conclusively determine the cause of symptoms, the study reveals that two-fifths of students and adults believe they set the volume on their iPods at "loud." Students are twice as likely as adults (13% vs 6%) to play such devices "very loud."

Adults, however, are more likely than students to use iPods and other brands of MP3 players (though not other portable devices) for long periods of time. More than half the adults polled use the players for one to four hours (43%) or longer (9%) daily. This figure may reflect the extended commute period during which adults listen. This puts them at great risk for cumulative hearing loss.

"Louder and longer is definitely not the way to use these products," says Brenda Lonsbury-Martin, PhD, ASHA's chief staff officer for science and research. "Eventually, that becomes a recipe for noise-induced hearing loss, which is permanent."

Speaking by telephone from Loma Linda University, where she serves as research professor in the Division of Otolaryngology—Head and Neck Surgery, Department of Surgery, Lonsbury-Martin told Stereophile that, as an alternative to conventional earphones, the study endorses the "sound-isolating earphones" produced by Shure and Etymotic. According to the poll, 77% of surveyed students and 81% of adults have not purchased such earphones.

Both companies' devices come equipped with flanges, flex sleeves, and/or foam sleeves that form a relatively tight seal in the ear, enabling users to reduce noise from the environment without having to turn up the volume as high as with conventional earphones. (I can vouch for the pricey—$500—Shure E5s. When connected to my PowerBook, they do a fine job of shutting out airplane noise, conveying a pleasingly mellow treble as well as ample midrange and bass.) Lonsbury-Martin and her colleagues have not yet checked out the noise-isolating or noise-canceling "earmuff" headphones from Bose and other companies.

"We know what can happen when one listens at high intensity for extended durations," she said. "We've done a lot of research in industrial situations. We also know the volume levels these portable devices are capable of producing."

Most alarming is the industry trend to target younger and younger children with portable listening devices. Disney is currently marketing its Mix Stick, an MP3 player available at Best Buy, to what Lonsbury-Martin terms "the Cinderella and Snow White crowd." "These devices output the same levels of sound as devices marketed to adults," she says. "It's scary."

Somewhat more comforting is Lonsbury-Martin's view that the type of damage MP3s can inflict is minimal unless the user spends 40–50 years listening at levels often endured by those in metal stamping plants or the military. This does not mean, however, that the ability to enjoy music will remain unimpaired.

"Psychophysically, we do not know how the brain translates acoustic energy into music," says Lonsbury-Martin. "It's all taken apart and put back together. Without knowing how the brain does it, we don't know how to make electronics that will mimic the process."

At present, neither hearing aids nor cochlear implants seem adequate for the high-quality enjoyment of music. Cochlear implants, which replace the structure in the inner ear that converts sonic energy into impulses the brain recognizes as sound, do not convey the full sonic spectrum. They may enable recipients to carry on conversations or talk on the phone, but they fall far short where music is concerned. Though researchers are currently trying to improve hearing aids and cochlear implants, their success has been hindered by a lack of scientific research.

Several other findings from the poll bear repeating. Among students, African-Americans and Hispanics are more likely than Caucasians to acknowledge that they have experienced at least some symptoms of hearing loss. Teenage boys, who listen for longer periods and at higher volumes than teenage girls, are more likely to use the products surveyed in ways that may cause later hearing loss. While a majority of parents (59%) are concerned about hearing loss in their children from the use of these devices, fewer than half are willing to limit the amount of time their children use them.

Besides lowering the output on portable devices and changing listening habits, Lonsbury-Martin urges people to monitor their hearing. "When you think your hearing is changing on you," she says, "it is time to limit volumes and intensities, especially the duration you listen at loud levels."

The poll asked teenagers and adults the best way to convey messages about potential hearing loss. Both adults (32%) and teens (43%) feel that television provides the best means for reaching teens. For boys, television is by far the best (50% vs 36% for girls). Girls are six times as likely as boys to say that teen magazines are a good source of information.

Unfortunately, television ads are so expensive that, unless ASHA can partner with other organizations or perhaps manufacturers, they are not feasible at this time. It will be interesting to see if future litigation impels manufacturers to pay for such ads, or at least to print large warnings, similar to those required of cigarette manufacturers, on all advertisements and literature.

The complete survey is available here.

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