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New hearing conservation initiatives: Small steps with great potential

Bloom, Sara

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doi: 10.1097/01.HJ.0000286240.48687.b1
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Afew months ago, The New York Times reported that the parents of children in Public School 234, an elementary school in Manhattan, had succeeded in getting the developer of a 162-unit apartment building under construction behind the school to pay for $2 million in noise-abatement measures. The parents had hired an acoustical engineering firm to determine an acceptable noise level for a construction site near a school, and spent 9 months negotiating with the developer. In the end, the developer agreed to erect a 20-foot-high sound barrier and to use hydraulic rather than conventional pile-driving hammers to keep noise levels low.

The story indicates that members of the public sector—admittedly, in this case, a fairly wealthy sector with determination and means—have heard the noise-can-be-dangerous message and are heeding its warning. This should be welcome news to hearing conservationists, who have been trying for decades to get people to understand that excessive noise can lead to hearing loss. Less successful, however, it would seem from the Times article, are efforts to persuade developers, factory owners, and others who create noisy environments that these sites are potentially harmful and should be addressed.

Without federal intervention from the Occupational Safety and Health Administration (OSHA) and other government agencies—or concerned private citizens in the New York City school example—harmful noise in the workplace likely would go unchecked. And, says Thomas Thunder, AuD, an audiologist and acoustical engineer with Acoustic Associates, Ltd., of Palatine, IL, far too little is being done to reduce noise in the workplace. After all, he says, why should a company go to the expense of implementing expensive engineering controls when oversight agencies are satisfied that simple earplugs or earmuffs can provide adequate protection for workers? At present, says Thunder, there is little incentive to control noise.

According to the National Institute for Occupational Safety and Health (NIOSH), 30 million workers in the United States are exposed to hazardous noise, that is, simply put, noise that exceeds an average of 85 dB over 8 hours (or higher levels for shorter periods of time). Exposure to excessive levels of noise may cause hearing loss, create physical and psychological stress, reduce productivity, interfere with communication, and contribute to accidents and injuries by making it difficult to hear warning signals. This article will look at new hearing conservation initiatives to reach out to industry and the public, report on some of the newer hearing-protection devices on the market or in development, and provide an update on research on ways to help people protect their hearing now and in the future.

ORGANIZATIONS PROMOTE THE LESS-NOISE MESSAGE

Laurie Wells, MS, is president of the National Hearing Conservation Association (NHCA). When it began in 1976, the organization concentrated on hearing loss stemming from occupational exposure to noise. More recently, Wells says, NHCA has broadened its focus to be more proactive in preventing noise-induced hearing loss in industry and the armed forces and is branching into consumer and recreational areas. “If it has to do with preventing hearing loss, we are involved,” she says.

Two NHCA task force groups are reaching out into communities, and the association has formed an alliance with OSHA to develop educational tools for employers and employees. These so-called eTools, one for combating noise-induced hearing loss (NIHL) and another to help employers accommodate the needs of hearing-impaired workers, are posted on the OSHA web site, www.osha.gov.

Wells, who is director of audiology for Associates in Acoustics, Inc., a consulting firm in Evergreen, CO, knows first-hand how unpleasant noise, even at acceptable levels, can impact daily living. A few months ago, she visited New York for the first time for a conference hosted by the Audio Engineering Society. While New Yorkers are used to the usual background cacophony of street sounds—fire, police, and ambulance sirens, honking horns, and the incessant rush of traffic—the Colorado resident said she needed hearing protection to get to sleep. “You can shut your eyes, but you can't shut off your ears, even when you're trying to sleep,” she says.

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Figure:
Laurie Wells

Her experience brings home an important point about noise: In addition to its potential threat to hearing, it is responsible also for increased stress, communication difficulties, and diminished quality of life.

Task Force on Children and Noise

Deanna Meinke, MS, an assistant professor of audiology and speech language sciences at the University of Northern Colorado, has headed NHCA's Task Force on Children and Noise for 6 years. Aimed primarily at calling attention to the dangers of loud noise, the task force reaches out to teachers, parents, scout troops, churches, and other community groups that influence children in its efforts to encourage young people to protect their hearing for their health.

Loud music, firecrackers, firearms, movies, motor bikes, sporting events, squeaky toys—all can affect a child's hearing, Meinke says, quoting a study estimating that 5.2 million youngsters in this country have a hearing loss that may be noise induced. Meinke believes that when children are instructed to protect their hearing, they develop a healthy hearing habit that stays with them throughout their lives. The goal is not to keep children from participating in activities they enjoy, she says, but to be sure that their hearing is protected while they're doing so. According to Meinke, young children accept and respond positively to hearing health information, whereas adolescents and adults are more resistant. “We tend to take hearing for granted,” says Meinke. “We need to upgrade the value of hearing, and the best place to start is with our children.”

Seeking a larger audience

The task force has many ideas for programs, but is still uncertain how to usher them onto a national stage. Should it be through public health agencies? School systems? Parent support groups? And how will large-scale programs be funded? These are questions the task force is still pondering. In the meantime, its smaller initiatives are producing positive results on local fronts.

  • In Colorado, the task force obtained a state grant to provide substitutes in two school districts so that 20 staff teachers could attend a workshop on how to integrate the dangers of NIHL into the science curriculum.
  • The task force traditionally sponsors a teacher outreach program in the city where the annual NHCA conference is held. This year's conference will be held February 16–18 in Tampa, FL.
  • The task force is aligned with an Oregon program called Dangerous Decibels, a public health campaign begun 6 years ago in Portland. Dangerous Decibels offers a K-8 classroom program on the perils of excessive noise, and has mounted an interactive exhibit at the Oregon Museum of Science and Industry that teaches children about dangerous sounds and their consequences.
  • The task force is working with William Martin, PhD, director of the Dangerous Decibels program, to distribute a noise-education kit. Each kit will contain a reference CD, tuning fork, sound level meter, text, photos, and suggested activities, and sell for about $75, or less if an underwriter can be found, Meinke says.
  • In collaboration with the American Academy of Audiology (AAA), the NHCA task force has produced a brochure for parents and teachers called Crank It Down, a how-to guide for protecting children's hearing from noise. (The brochure can be downloaded at the NHCA web site: www.hearingconservation.org.)
  • Finally, the task force will hold a conference November 19–20 in Cincinnati focusing on children's hearing health.

Task Force on Music-Induced Hearing Loss

Another NHCA task force addresses music-induced hearing loss (MIHL). Chaired by Brian J. Fligor, ScD, director of diagnostic audiology at Children's Hospital in Boston, this task force was formed in 2004 at the request of the Audio Engineering Society, which was concerned that people like themselves, who monitor and evaluate the quality of sounds, were at risk for MIHL—potentially an occupation-ending injury.

Audio engineers, band directors, and other professionals working in the music and audio industries are a small segment of society, not subject to the same scrutiny as current OSHA-regulated industries, Fligor says. However, he points out that “those affected are responsible for [our] entertainment. If we lose these people, it impacts all of us.”

The task force head notes that many sound professionals reject ear protection on the grounds that sound is distorted when attenuated and the distortion cuts down on the enjoyment of sound as well as the ability to hear sound optimally. In trying to influence the music and sound communities, the task force submits articles to professional journals identifying the risks of MIHL and recommending acceptable ear protection, such as flat-frequency hearing attenuators that reduce volume without distorting audio quality. “If we can satisfactorily reconcile the benefits of adequate protection and optimal performance, we can increase the longevity of the audio professional's career,” Fligor says.

As with the Task Force on Children and Noise, this task force is working on a local project with the potential to reach a national audience. The University of North Texas, in Denton, TX, has adopted a safety and instructional activities policy guideline for the school's music ensembles. Among other components of the policy, the guidelines contain information on how to teach students to reduce the risk of hearing loss. Kris Chesky, PhD, a member of the university's music faculty and of the task force, will present the university's new policy to the National Association of Schools of Music, to which 650 accredited schools belong. Says Fligor, “What if this were to become a standard of the accrediting body?”

Concertgoers also need protection

Musicians and sound technicians are not the only ones who need protection from music exposure, says David Opperman, MD, chief resident in the Department of Otolaryngology at the University of Minnesota Medical Center. Opperman is the principal investigator of a study showing that concertgoers also are at risk for NIHL. For the study, Opperman and his co-authors asked 29 volunteers to attend three concerts—pop, rock, and heavy metal—in the same concert hall. Sound levels, which averaged 99.8 dB and peaked at 125.6 dB, emanated from amplified music as well as crowd noise, Opperman says. Participants without earplugs demonstrated significant threshold shifts in all three music genres and in all five seating positions tested. Likely, the hearing shifts among the participants in his study are temporary, Opperman says, but NIHL is cumulative, and over time exposure can lead to permanent hearing loss.

In addition to its main goal—determining if concertgoers are at risk for hearing loss—this study confirmed other theories related to NIHL. First, the researchers found strong resistance to ear protection. Opperman says it was difficult to find willing volunteers for the earplug control group of the study. Additionally, 27% of those wearing earplugs still experienced a significant threshold shift, proving that earplugs can protect hearing only if they are inserted properly and fit well. “Because you're wearing an earplug doesn't necessarily mean you are protected,” Opperman says.

Other organizations are also involved

The League for the Hard of Hearing, founded in New York City in 1910, is one of the nation's oldest non-profit agencies treating deaf and hard-of-hearing children and adults. The league sponsors a number of programs that promote hearing conservation and also serves as a hearing health information resource for schools and community groups. Much of its work is centered in the New York area, but recently it is broadening its focus, says Amy Boyle, the league's director of public education.

  • The 11th annual International Noise Awareness Day will be held on April 26. Developed by the league as a local event, it is now recognized in other U.S. cities and in a few cities abroad. Over the years, Noise Awareness Day has generated substantial media coverage, including newspaper articles and radio and TV appearances by league personnel, who discuss the dangers of NIHL to the general public. Free materials about the 2006 event are available at www.lhh.org.
  • Recently, the league conducted a “noise tour” of the United States to demonstrate that no matter where you live or work, you may be exposed to noise that's hazardous to your hearing. The tour stopped in New York, Los Angeles, Minneapolis-St. Paul, San Francisco, St. Louis, Chicago, Fort Lauderdale, FL, and New Haven, CT. Decibel readings were recorded in restaurants, nightclubs, beauty salons, video arcades, subways, schoolyards, and even in libraries. Sound levels were also measured on city streets and at construction sites. Among the findings were that dinner crowds are noisier than lunch crowds, that St. Louis has the quietest library, and that beauty parlors are, by and large, noisier than subways. The highest readings—115–120 dB—were recorded at a nightclub, at a construction site, and in city traffic with sirens blaring, all three in San Francisco.
  • Over the summer, the league partnered with Etymotic Research for a program at a rock and roll camp in upstate New York. Etymotic donated earplugs, and the league told the dangerous noise story to youngsters and their counselors.
  • In August 2005, New York City Mayor Michael Bloomberg called on the City Council to overhaul the city's noise code. The mayor noted that noise is the number one complaint to the citizen service hotline, generating more than 410,000 calls in the previous 14 months. The League for the Hard of Hearing advised the city on the revisions, which would require noise-abatement measures at construction sites; restrict the level of music from bars, clubs, and cabarets; set a decibel level standard for air conditioning units; and establish common sense standards for car stereos, loud music, barking dogs, and loud mufflers. The proposed rules would also prohibit sound from any source that raises the ambient noise in a residence by 10 dB during the day or 7 dB at night.

“The League's efforts are often grass-roots,” says Boyle, “but over time, we are helping more and more people protect their hearing health. We are breaking down the barriers to hearing protection, making it more mainstream.”

A federal program

While NHCA is expanding its efforts, Laurie Wells says, “We have left the public campaign work to bigger organizations with more resources to do it more effectively.” One such program is Wise Ears, a campaign sponsored by the National Institute

on Deafness and Other Communication Disorders (NIDCD) and NIOSH, among others in the coalition of agencies working to combat NIHL.

Through articles in print media, videos, flyers, fact sheets, brochures, and radio spots, Wise Ears seeks to increase awareness of the dangers of noise and to promote the use of hearing protection and hearing conservation in the workplace. Since its inception in 1998, Wise Ears has generated more than 1200 media articles reaching more than 100 million readers.

AN UPDATE ON HEARING PROTECTION

Hearing protection devices, like earplugs and earmuffs, are the most practical and convenient way to protect against NIHL. However, getting people to wear hearing protection is another story, says Elliott H. Berger, MS, senior scientist in auditory research at the Aearo Company in Indianapolis. The industrial market, such as auto and aircraft manufacturers, and the United States military require that hearing protection be worn to comply with OSHA standards. But the consumer market, which is unregulated and requires voluntary action, is “a tough go,” Berger says. “It's not unusual for people to carry sunglasses with them in case the weather turns bright, but most people don't carry hearing protection with them in case they find themselves near a construction site or in a loud club or seated near the band at a social function.”

To complicate matters, it's not easy for consumers to purchase protection. It's not that earplugs aren't available in hardware and home improvement stores or drugstores and pharmacies. They are. They come in many different styles, each marked with an NRR (noise reduction rating), a number that, unfortunately has little bearing on the product's actual noise-reduction effectiveness in the real world. (The NRR is determined in ideal conditions in a laboratory setting.)

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Figure. E:
lliot Berger

OSHA reduces the NRR by 7 dB and then by half of the remainder. So, if a hearing protector has an NRR of 25 on its packaging, it's actual noise-reducing value is 9 (25-7×1/2). But, as most consumers don't know that formula—or even what NRR stands for—it's hard for them to know which noise protector is appropriate for a particular application.

To be on the safe side, a buyer could choose the device with the highest number. But then, the consumer might get too much protection, with the result that the person's hearing is so compromised that speech and music are inaudible. In a worst-case scenario, this might even be dangerous. Suppose that when wearing earplugs, the person can't hear a warning from a signal or a co-worker. People won't wear protection if it interferes rather than helps. That's why Elliott Berger and others in hearing conservation say the best protection is the one that's worn.

So, which one to wear? The HJ 2005 World Directory lists 177 companies under the heading “Hearing Protection Devices and Supplies.” Most of the products listed fall into five basic models, although these come with dozens of variations offered by various manufacturers. The basic models are foam plugs, pre-molded soft plastic plugs, and headbands with small earbuds, generally available in consumer stores.

Then there are custom earplugs, which require impressions to be taken by a hearing professional and cost much more than non-custom devices. Finally, there are earmuff models, some of which are sold over the counter, while others, often with special features, are available only through professional sources.

New hearing protection products

Berger of Aearo described two hearing protection products recently introduced to the market: one for military and law enforcement use, the other for industrial use. In the military/law enforcement application, either end of a single plug can be inserted; one end allows low-level sounds to reach the ear, but reacts instantly to filter out sudden blasts, such as gunfire or explosions. The other end of the plug offers protection against steady, high-level sounds. Essentially, the plug provides two types of noise protection, Berger says, noting that the dual-end design will soon be introduced into the recreational market for use by hunters, among others.

Product developers have found that factory workers wearing an earmuff device must lift the ear cup of the unit to hear a low-level sound, like a human voice. However, lifting the cup exposes the ear to high-level ambient noise and defeats the purpose of the protective device. So now, Aearo offers electronic earmuffs that come equipped with a microphone embedded in the earcup to pick up softer sounds and transmit them to the wearer through the earmuff. Thus, the amplified sound is limited to a safe level.

Another product popular with people wishing ear protection is an earmuff with a built-in radio. Berger says the radio diminishes the effectiveness of the protection somewhat, but it allows the wearer to feel connected to the real world, rather than cut off by his or her hearing protection.

Protecting musicians' hearing

Mead C. Killion, PhD, president of Etymotic Research in Elk Grove Village, IL, is well known as the developer of the ER series of earplugs for musicians, a group, he says, who need ear protection but are often unwilling to use it.

Killion says the Musicians' Earplug came about because of the French composer Hector Berlioz. During a performance of Berlioz's Damnation of Faust in 1989, Bob Swan, a violist in the Chicago Symphony Orchestra, was seated in front of the brass section. At the end of the concert he couldn't hear conversations or normal music. He needed a course of steroids to get his hearing back, and the importance of protection—for all musicians, classical as well as jazz and pop—became apparent.

The challenge for Killion was to create an earplug that would provide high-fidelity sound while excluding noise. His solution was the custom-made ER-9, followed by the ER-15, and now the ER-25, which provides 25 dB of attenuation, making it appropriate for drummers and musicians in high-intensity rock groups.

Ear protection vs. noise reduction

Thomas Thunder of Acoustic Associates, Ltd. leads a 3-day course and a 1-day brush-up for the Council for Accreditation in Occupational Hearing Conservation (CAOHC). The course certifies or recertifies participants—mostly audiologists, medical technicians, nurses, and support staff—to conduct an audiometric, pure-tone, air-conduction test to monitor the hearing of persons exposed to noise.

In addition to proper procedures for conducting the test, Thunder's course covers strategies for assessing noise and protecting hearing from excessive sound levels. But it does not address how to reduce noise in the workplace. “CAOHC doesn't require that,” Thunder says. He explains that in the 1970s and 1980s, OSHA shifted its emphasis from requiring engineering controls to reduce noise to mandating ear protection to preserve hearing, leaving little incentive to undertake expensive repairs. He acknowledges that most industrial noise does not exceed 110 dB, which supports the argument that wearing hearing protection is an adequate response to noise. “But,” he asks, “if people supposedly have proper protection, why do we see so many worker compensation claims for hearing loss?”

RESEARCH: ON THE HORIZON

Regeneration of hair cells

Exciting research in the field of NIHL is under way. One of those in the forefront is Yehoash Raphael, PhD, an associate professor of otolaryngology at the University of Michigan's Kresge Hearing Research Institute in Ann Arbor. His team has succeeded in using gene therapy to grow new auditory hair cells and restore hearing in deafened adult guinea pigs.

The group injected a gene called Atoh1, a key regulator of auditory hair cell development, into the ears of 10 guinea pigs, whose hair cells had been destroyed by large doses of ototoxic drugs. Microscopic images of the inner ears treated with Atoh1 8 weeks after inoculation showed large numbers of hair cells in the cochlea. “This is the most exciting finding of our study,” Raphael says, adding that he repeated the tests four times to be sure of his results.

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Figure:
Yehoash Raphael

In future research, Raphael plans to test Atoh1 treatment in aged animals and animals deafened by noise exposure. He says it will be several years before Atoh1 gene therapy is ready for human testing; nevertheless the research promises to be a major step forward in the search for new ways to treat hearing loss.

Otoprotective agents

Kathleen C. M. Campbell, PhD, is professor and director of audiology research at Southern Illinois University's School of Medicine in Springfield. Campbell is also a researcher and lecturer, focusing on ototoxicity and NIHL. She holds two patents for otoprotective agents and is preparing for clinical trials.

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Figure:
Kathleen Campbell

In an article published last year by the ASHA Leader Online, Campbell writes, “…there is an intense search for agents that could protect or rescue cochlear hair cells from excessive noise exposure. Although no drugs are currently approved by the U.S. Food and Drug Administration (FDA) to prevent or treat NIHL, several hold promise.”

“The most promising agents approaching clinical trials appear to be D-methionine (D-Met), acetyl L-carnitine (ALCAR), and N-acetyl cysteine (NAC). All three show good protection in animal studies when administered before noise exposure, although D-Met and ALCAR have shown somewhat better hair cell protection than NAC. D-Met and NAC also show some efficacy in preventing permanent NIHL when administered within 1 hour after noise exposure.” In addition, Campbell told HJ, ebselen is a promising otoprotective agent nearing FDA clinical trials.

Campbell says that the damage from some sudden, unexpected noise exposures, such as cannon blasts or a car exploding, cannot be avoided. However, by controlling free radicals in the body through a healthy diet and lifestyle, one can reduce the risk of NIHL. It stands to reason then that “antioxidants that detoxify free radicals may also protect against NIHL,” she says.

Campbell predicts that in 5 to 10 years, there will be drugs to reduce the risk that hearing loss caused by loud noise will become permanent. Nevertheless, she predicts, no ingested substance will replace hearing protectors.

The Hearing Pill

David Karlman, chairman and CEO of American BioHealth Groups, LLC, in San Diego, agrees that an otoprotective agent is not a substitute for earplugs; this is complementary technology, he says. On the other hand, American BioHealth Groups holds the distribution rights to the Hearing Pill, developed by military researchers, which, he says, “enhances the defense mechanism of the cochlea before an acoustic or toxic insult, and enhances the reparative capabilities of the cochlea after acute injury but before permanent injury is established.”

Karlman notes that the U.S. Army and Navy have been working on this technology for 8 years. Thirty percent of battle injuries are head trauma, he says, and about 16% of those injuries cause hearing loss. Karlman says that last year alone, the U.S. military spent $800 million on hearing loss compensation.

The clinical study for the Hearing Pill, conducted on 566 marines, resulted in a “positive biological effect that reduced the incidence of permanent hearing loss,” Karlman says, noting that the study's science will be published early in 2006. In the meantime, the Hearing Pill is being sold on the Internet (www.abgpharma.com) at $34.95 for 95 tablets, and eventually, Karlman says, will be sold over the counter.

NAC, which is the Hearing Pill's main ingredient, has not been approved by FDA for prevention or treatment of hearing loss. However, American BioHealth counters, the agency has approved NAC as a safe and effective treatment for other indications. Karlman adds, “The Hearing Pill is a nutritional supplement, not subject to FDA regulation.”

Noise protection as fashion statement

Finally, there is a company hoping to tap into the consumer market through an unusual product line called HearWear. According to the company's web site (www.absurdee.com/hearwear), HearWear is “an experimental integration of technology and fashion design.” There is only one HearWear prototype product so far, a skirt that reacts to environmental noise. Electronics in the garment detect noise and light up in patterns that respond to the level of sound. The company that developed HearWear is named Absurdee.

FINAL THOUGHTS

This article only begins to touch on the diverse efforts by hearing health organizations, individual practitioners, and researchers to call attention to and remediate the damaging effects of excessive noise exposure. As this article suggests, it is an uphill battle.

Certainly there has been progress in recent years. On the other hand, new sources of NIHL are constantly emerging. For example, the popular iPod can be harmful if the user cranks up the volume too high. The only checks on personal stereos are the user's own good sense and the efforts of hearing professionals to get the NIHL message across.

There is a common perception, says Thomas Thunder, that “hearing conservation is a specialty.” But, he adds, “Hearing conservation should be at the core of what we all do.”

“We spend millions helping people to hear after they've lost their hearing,” says Mead Killion. “Preserving hearing is a much higher calling.”

© 2006 Lippincott Williams & Wilkins, Inc.