Hearing loss is easy to ignore. There is usually no pain, no pressure and no bleeding as hearing loss from noise exposure occurs.
"Things that happen gradually, such as hearing loss, are easily ignored until it is too late," said noted audiologist Maurice H. Miller, Ph.D. "If a drop of blood came out of our ears every time we heard a noise that was loud enough to injure our hearing, we would find hearing loss difficult to ignore."
There are an estimated 33 million people in the U.S. with hearing loss severe enough to affect their daily activities. Noise exposure, a significant amount of which is occupationally related, accounts for 11 million cases of hearing loss. And there are another 36 to 37 million people who suffer from tinnitus, which is a chronic ringing in the ears.
Noise does more than harm hearing ability. According to Miller, workers identify noise as the most unpleasant and annoying contaminant in their work environments. Noise compromises the character of the work environment, said Miller, and can lead to reduced productivity and increased anxiety and stress for workers.
Research has also linked high noise levels to: increased workplace accidents (due to communication problems between workers); decreased productivity; and reduced ability to reason, solve problems, finish assignments and be accurate. Noise can also isolate workers, a big problem among work forces that need to act as a team to perform job tasks.
Fortunately, there are many products in the marketplace which can protect hearing, allow for communication between workers and reduce noise levels. Before you choose a solution to fit your particular situation, you must first determine if noise is a problem for your workers.
There are indications, in the absence of actual measurement of noise exposure, to determine if your workplace has a noise problem.
- Workers report tinnitus for various periods of time after they leave the workplace.
- Workers have difficulty communicating and are forced to scream at each other.
- When workers leave after an 8-hour day, they have difficulty hearing and understanding speech. Miller said these workers suffer from "consonant discrimination and word recognition," which means that words like pit, kit, fit and sit all sound alike.
If any of these three factors exists, then there is a problem and a noise survey can document the need for an occupational hearing conservation program (OHCP).
A noise survey uses information gathered from two sources: sound level meters used to monitor the noise level in the workplace, and dosimeters worn by employees to measure their personal exposure to workplace noise. They should be conducted every two years, more often if a change in production, processes, equipment or controls increases or changes employees' exposure to noise.
The Occupational Safety and Health Administration (OSHA) has set what is called an "action level": the noise level at which an employer must take action to protect the hearing of his workers.
Action levels depend on the noise level and the time spent in noisy environments. The action level that appears to impact the most workplaces, said Miller, is a level of noise exposure of 85 dBA for a time-weighted average of eight hours.
There are instances, he noted, when noise levels higher than 85 dBA are allowed before an action level is reached. As the noise level increases, however, the allowable exposure time decreases. Miller called this a "time/intensity trade-off." For example, exposures up to 115 dBA for a steady state of noise are allowed, but only for a total of 15 minutes in any eight-hour period.
If an action level is reached, then OSHA requires that an employer implement an OHCP. The first step in any OHCP is to test the current hearing ability of employees.
Audiometric testing reveals what impact noise exposure has on the ability to hear sounds, and can be used to document the long-term impact noise exposure has on employees. It also sets a baseline for new employees so the effect of workplace noise exposure can be accurately evaluated.
An employer cannot force employees to take audiometric tests, but they must make them available. Make employees aware that the tests are used to protect and preserve their hearing, and are part of your company's safety and health program, said Miller. Once employees realize that such testing can be used to develop OHCPs which help to prevent hearing loss, most agree to the tests.
If hearing shifts are discovered among workers, or if action levels are reached, then employers must move to reduce noise levels and/or noise exposure. OSHA requires employers to target three specific areas to reduce employee exposure to harmful sound levels.
Engineering controls are considered the first line of defense against high noise levels because they can eliminate or reduce noise at the source. Such controls might include proper maintenance of machinery to eliminate excessive noise; mufflers, noise bafflers or enclosures for noisy equipment; placement of noisy machinery in areas of the facility which are away from employees; placing visual as well as audio warnings or cues on machinery; or "buying quiet" programs, which seek out machinery designed to work more quietly.
If engineering controls are not feasible due to cost considerations or the nature of the noise source, then administrative controls are suggested as a second line of defense. For example, schedule noisy operations throughout the day, rather than running them all at once, which can help to reduce the overall ambient noise. Other solutions may include reducing the number of employees in a noisy area or running the loudest operations at times when the fewest employees are working.
The last line of defense is hearing protection. "This involves more than handing earplugs or earmuffs to employees and telling them to wear them," said Donald C. Gasaway, a hearing conservation specialist for Aearo Corp., Indianapolis.
When he began his career in hearing conservation, there were "a dozen or so" types of hearing protection. Now, there are over 371 models of hearing protection devices.
"It is wonderful that there is a broader range of protection available," said Gasaway, "but it means that safety managers have a greater responsibility, a real challenge to choose the best hearing protection for their workers."
Adequate protection is obviously needed, but Gasaway warned that workers who are overprotected are "handicapped," and compared hearing protection to sunglasses. On a sunny day, sunglasses can help reduce glare and improve vision. However bright the sunshine, though, welding goggles, which are so dark they are almost opaque, would not be appropriate protection. They would probably be more of a hazard than no protection at all. The same is true of too much hearing protection.
"If employees cannot communicate with each other in a noisy environment, what do you see?" Gasaway questioned. "You see them remove their earmuffs or earplugs in that noisy environment. In most cases, a noise reduction rating of 10, 12 or 15 is appropriate to protect hearing and still allow employees to communicate and hear machine sounds and warning devices."
Safety managers need to examine the noise hazards and the work environment before choosing hearing protection for employees. Noise levels; temperature; the presence of particulates in the air; communication needs (which might require earmuffs with communication capabilities); workstation configuration; and whether or not the employee already has a hearing loss contribute to choice of protection.
Many earplug styles on the market offer similar protection capabilities. Miller said plugs should be chosen which provide the necessary protection factor, but he suggested offering employees as much input as possible as to the varieties kept in stock. That might mean having several different styles of earplugs available.
Placing anything in the ear is invasive, said Miller, and many employees must wear earplugs eight hours a day. Those earplugs should be as comfortable as possible
If employees move from office or low-noise environments to environments which require hearing protection, then the use of plugs which are attached by cords might be a good choice. When not in use, the plugs can hang by the cords around the necks of employees, making it easier for them to keep the earplugs clean and close at hand (rather than putting the plugs in and out of pockets or carrying them in their hands).
Employees who have already suffered some type of hearing shift should be given extra protection in the form of earmuffs, or be removed from the noisy environment, said Miller. In some high-noise situations, the use of double protection, in the form of both earplugs and earmuffs, might be appropriate.
Once appropriate protection is chosen, employees should be given instructions on how to place hearing protection over or in their ears; how to care for their hearing protection and when to replace it; and how to reduce the potential for ear infections related to improper use, storage or cleaning of hearing protection.
"Earmuffs and earplugs should be kept clean," said Jeff Birkner, CIH, vice president, technical services, Moldex Metric Inc., Culver City, Calif. "Don't reuse disposable items. Make sure your hands are clean before you place the hearing protection, disposable and reusable, in or over your ears."
He also said that reusable items, like earmuffs, should be inspected regularly. Look for cracks; make sure the tension band over the top is tight; check the foam in the ear pads to make sure it has not degraded over time; and check fittings to make sure they are not worn or cracked.
OSHA requires that employers provide employees with an education program at least once a year. In addition to nuts and bolts information like care and storage of hearing protection, the program should describe all aspects of the OHCP; the audiometric testing program; the dangers of noise exposure; and the relationship of noise to hearing loss and actual damage to the ears.
Finally, said Miller, remember the four "Ps" about occupational hearing loss: "It is permanent, painless, progressive and preventable."
"We can't monitor what people do in their homes," he said, "but we can protect them in the workplace. The hope is that the education they receive in the workplace will be remembered once they get past the plant gates."