September 24, 2005

Concert-Bound? Take Your Earplugs

Hearing loss can result, whether the music is heavy metal or pop, study finds

If you're a concert fan -- whether your taste is heavy metal or pop -- don't forget to take your earplugs.

If you don't, you risk damaging your hearing and eventually suffering noise-induced hearing loss. So says a new study to be presented at the American Academy of Otolaryngology/Head and Neck Surgery annual meeting, which begins Sept. 25 in Los Angeles.

The advice also holds whether you're in a front-row seat or the "nosebleed" section, said Dr. David A. Opperman, the lead investigator of the study and chief resident at the University of Minnesota's department of otolaryngology in Minneapolis.

"No seat is a good one without earplugs," he said.

In the study, Opperman and his colleagues assigned 29 men and women, who ranged in age from 17 to 59, to sit in a variety of seats while attending concerts featuring heavy metal, pop or rockabilly music. Two people were placed in each location -- whether front row, stage-left, stage-right, or far from the stage. One person in each location wore earplugs while the other did not.

Before the concerts, the study participants all had normal or near-normal hearing "thresholds," based on the results of a hearing test called an audiogram. A threshold is the softest sound you can hear on an audiogram.

After the concerts, when audiograms were given again, 64 percent of those not wearing earplugs had significant hearing thresholds shift, in which they couldn't hear a sound as soft as they could before the concert, compared to 27 percent of those wearing earplugs, the study found.

"A threshold shift is a decrease in the ability to hear as represented on an audiogram," Opperman said. "The ability to hear before the show was better than the ability afterwards."

The shifts occurred regardless of seat location or type of music. "The genre of music doesn't seem to matter," said Opperman. "The misconception that heavy metal is worse than pop puts the people at the pop concert at more risk."

When the researchers measured sound levels at the concerts, they found the maximum was 125 decibels. Prolonged exposure to noises about 85 decibels can damage hearing, according to the academy.

It not just the loudness of music at concerts that puts your hearing at risk -- crowd noise can be quite loud, too, Opperman said. "We observed the ambient noise from the crowd was more than ambient. It was significant," he said.

Other studies have found that noise levels from crowds at sporting events can reach 125 decibels, nearly the noise level heard at car racetracks, Opperman said.

It's not known whether the hearing loss experienced by the study participants was permanent, Opperman said, because the researchers didn't perform follow-up exams after the post-concert test. "That was partly due to the difficulty of getting them to come back in three months for [repeat] audiograms," he said.

"They may not have any permanent loss from that concert," Opperman said, but he added that accumulated damage can result in hearing loss.

Sigfrid Soli, a scientist at the House Ear Institute in Los Angeles, said the study is the first of this type that he has seen, but the results are no surprise. "The results are entirely predictable and expected," he said.

"If you have excessive exposure to noise, your inner ear gets tired and needs some time to recover," Soli said. "During this period of tiredness and recovery, depending on the extent of the noise exposure, you have a temporary increase in your hearing threshold."

Whether that will result in permanent hearing damage depends on how often, how long and at what volume of sound you are exposed to, Soli said. Experts debate the issue, he said. But research for the workplace has found that people exposed to sound levels of 85 decibels for an 8-hour workday for 40 years over their working life are at risk of hearing loss of 7.9 percent by age 60. "But if you go to 90 [decibels on a daily basis for that long], it goes up to 25 percent," he said.

Opperman said his study proves that earplugs work, though they are not perfect, as shown by the finding that even some of those wearing the devices had threshold shifts. "The earplugs may not have fit properly. Persons may not use them properly."

Many performers now wear earplugs, aware that prolonged exposure can damage their hearing, Opperman said. But getting concert-goers to use them can be a tough sell. "People don't want to wear them," he said. "Two people in the study randomized to wear earplugs refused and had to drop out of the study."

Opperman suggested that when buying earplugs, which are available over-the-counter, choose those that reduce noise by 21 decibels. Another option is custom-made earplugs, available from an audiologist, which can fit better and provide better protection than over-the-counter models, he said.

More information

For more on how loud sounds can cause hearing loss, visit the American Academy of Otolaryngology-Head and Neck Surgery (www.entnet.org ).