Incremental, Insidious, Forever
By Dan Birch
IT'S A HAZARD that's heard daily, but all too often, not heeded. Dangerous noise levels are a part of the job for approximately 30 per cent of the industrial work force, says Brian Myers, portfolio ma...
IT’S A HAZARD that’s heard daily, but all too often, not heeded. Dangerous noise levels are a part of the job for approximately 30 per cent of the industrial work force, says Brian Myers, portfolio manager for hearing products at 3M Company in Indianapolis, Indiana. “It is, by my reckoning, the most common safety hazard that exists in the workplace,” Myers offers.
There’s no shortage of hearing protection to choose from. Among these are earplugs, single-use, reusable and custom-fitted; ear canal caps; and earmuffs.
Unlike the consequences of some other hazards — falling and entrainment, to name a couple — noise-induced hearing loss (NIHL) isn’t in-your-face obvious. It’s incremental and insidious, leading workers to sometimes take a pass on protection, Myers suggests.
“Once damaged, hearing cannot be restored. Damaged hearing can affect job performance, health and productivity,” cautions the Industrial Accident Prevention Association in Mississauga, Ontario.
It’s for these reasons that employees and employers best take hearing conservation to heart. A full program to guard against hearing loss will include noise measurement, worker training, hearing tests for employees, noise controls and personal protective equipment (PPE), in keeping with Canadian Standards Association’s CSA Z94.2, WorkSafeBC notes in its guide on hearing protection.
There are any number of strategies to get earmuffs, earplugs and ear caps over, into and onto workers’ ears, but the most effective approach may be to get workers truly appreciating their hearing, Myers says.
Renee Bessette, marketing manager for Howard Leight by Sperian in Smithfield, Rhode Island, concurs. Commending workers who regularly use protection as appropriate can be a powerful tool for compliance, Bessette suggests. That approach can encourage workers to protect not only their own hearing — but that of others as well, she says. “Peer pressure does exist in the workplace. People want to feel good about what they’re doing.”
Sometimes, however, seeing is believing. And that’s where fit — the importance of which cannot be overstated — comes in. A recent innovation in hearing protection has centred on individual fit testing.
Personal fit testing has the potential to improve worker compliance, suggests Jeffrey Goldberg, president of Custom Protect Ear in Surrey, British Columbia, which makes custom-fitted hearing protectors. Too often, says Goldberg, workers are not convinced protectors will save their hearing and, as such, don’t concern themselves with wearing devices correctly.
Howard Leight and 3M are among the manufacturers that have released fit testing systems onto the market. Howard Leight’s system “consists of software and an optimized headset, and utilizes a three-part process to determine the effectiveness of an employee’s earplug fit over a range of frequencies,” notes information from the company. “The result, known as a personal attenuation rating, identifies the actual protection an employee receives.”
Another technology intended to shed light on individual attenuation is personal noise dosimetry. Last fall, Bessette says Sperian acquired doseBusters USA, a maker of in-ear dosimetry, and will soon release a new personal dosimeter to the market.
Sperian reports that doseBusters technology “integrates traditional occupational hearing protection (earplugs or earmuffs) with personal noise dosimetry to provide real-time monitoring, measurement and documentation of an individual’s actual noise exposure.”
Myers and Bessette agree comfort is another key factor driving compliance. If a worker doesn’t care for the feel of earplugs, for example, he is less likely to use them, Bessette says.
The comfort challenge may be better met by offering hearing protection options to suit the differences and preferences that will inhabit any work force. “It’s important to have a variety of styles and materials of your earplugs to offer to your employees, so everyone can feel comfortable,” Bessette says.
For earplugs, the WorkSafeBC guide recommends pulling backward at the ear to straighten the ear canal, which will allow proper insertion.
Comfort is critical because most devices on the market will achieve the necessary level of attenuation, says Myers, but that demands they be worn properly.
Equipment size and weight will influence the pressure exerted by the gear, he says. “You don’t want that pressure to be objectionable.”
For earplugs, pressure is exerted in the ear canal; for earmuffs, the push is to the sides of the head.
Of course, some pressure is needed to achieve an effective seal. “The most common problem with earplugs is that they are not seated deeply enough in the ear canals. Partial insertion results in poor noise reduction, poor retention and discomfort,” WorkSafeBC reports. When properly inserted, “there will be a slight sensation of pressure, and the wearer’s voice will sound louder and more resonant.”
Myers says his company’s bid to address pressure has included creating reusable earplugs that have rearward sweeping contours rather than disc-shaped flanges. This establishes “more sealing surface area, and that inherently reduces the pressure that you create on any one spot,” he points out.
The lengths to which people will go to improve comfort is alarming and may be dangerous. To reduce objectionable pressure, people have cut off the flanges or bent the head band on earmuffs, Myers reports. The result, in both cases, is a reduction in the level of intended attenuation.
The selection of protective equipment “really depends on the environment of intended use,” suggests Kristin Libby, marketing director for Moldex-Metric, a hearing protection manufacturer based in Culver City, California.
Take, for example, a construction worker. Jeffrey Birkner, the company’s vice-president of technical services and quality assurance, says that either earmuffs or earplugs may provide the protection required, but the former may be desired during winter.
And what about managers and others who are exposed to low-level noise only intermittently? Ear canal caps are a promising alternative since they cover the ear canal opening, but do not fill the canal, allowing for easy removal.
Earplugs and earmuffs, however, are the main players. Earmuffs often provide a wider range of attenuation because, unlike earplugs, they don’t fill the ear canal, Bessette suggests.
The presence of airborne contaminants is an environmental factor that also needs to be taken into account. Myers cautions that reusable earplugs containing thermo-plastic elastomers, for example, are not suitable for workers who may encounter oil mists because the gear could “swell up and distort.”
And when it comes to equipment colour, final choice may be based on everything from whim to the need to be seen. Transportation, construction and airport ground crews are just a few of the workers who might fall into the latter category, says Bessette. “We would recommend a high-visibility earmuff that has the bright green ear cups and a reflective head band,” she adds.
Earplugs typically come in three varieties: single use, reusable and custom-moulded. Foam models cite a noise reduction rating (NRR) of as much as 33 decibels (dB), though the actual level of attenuation achieved may be considerably less after de-rating (see “Clarifying Matters” on page 48).
Single-use earplugs can be rolled and compressed between the user’s fingers before insertion. This may be great for speed and comfort, but less than ideal for dirty environments.
Myers is a fan of earplugs that feature a “slow-recovery” foam tip and a sturdy stem. The model marries the benefits of single-use and reusable earplugs, he says, namely higher attenuation and improved hygiene.
Reusable models can be washed with warm water and soap to be used more than once. Of course, this
protective option will not last forever.
As a rule, says Bessette, reusable earplugs are good for as long as four weeks. Despite that ball park, gear still needs to be inspected daily for tears, cracks and reduced pliability, she advises.
Custom-moulded earplugs are also reusable, and fill an important need in the protection market, Goldberg says. The key benefit is that fit — and, in turn, attenuation — is better than with foam and reusable options, he says. A mould of a worker’s ears is taken and a custom-fitted protector is then created that is “as personal as a finger print.”
While the company’s protectors are good for as many as 10 years, Goldberg recommends they be used for no more than half that time since physical changes within an individual’s ear will reduce attenuation. “The fit of the hearing protector becomes more and more comfortable, but it’s actually becoming less and less effective,” he cautions.
Sometimes, one type of gear is simply not enough. Dual protection — using earplugs and earmuffs together — is seldom called for, apart from the loudest of circumstances, including some mining operations. Still, Myers says the approach is appropriate for noise levels of 105 dB or more.
Dual protection does boost attenuation, but by how much? “There’s all kinds of rules of thumb,” Goldberg says, noting that common approaches include adding five decibels to the highest NRR or adding 10 per cent to the actual attenuation of the more powerful hearing protection device.
Again, though, the issue of comfort comes into play, says Goldberg. “Dual protection is uncomfortable. You’ve got all the pressure of the earmuff squeezing on the head combined with the pressure of the earplug pushing in the ear canal. It’s nobody’s idea of a good time,” he says.
Apart from comfort, workers must be mindful of wearing too much protection, Libby cautions. “The user has to be able to hear warning signals. If they can’t hear warning signals, this can be a clear and imminent danger,” she says.
“The ability to distinguish alarms, approaching machinery and conversational speech are vital aspects of safe performance on the job,” notes information from Custom Protect Ear.
Manufacturers have created various filters for hearing protectors to let through critically important noise, such as voices and alarms.
Myers points to reusable earplugs developed by his company in partnership with the United States military. The earplugs guard against loud, impulsive noise like weapons fire, but allow users to clearly hear voices and other low-level sound, he says.
The technology has industrial applications, too, Myers reports, saying it is now being used to protect against the explosive sound produced in electric arc incidents.
Howard Leight also employs filters that block hazardous noise, but not speech. “You don’t have to remove the hearing protector to have a conversation with somebody,” Bessette says of the protective gear.
Custom Protect Ear, for its part, can fit various filters into custom earplugs according to customer need, such as earplugs that are compatible with radio communication.
“We can take the incoming audio from the radio, right to the hearing protector and connect it so that you hear it in your ear,” says Goldberg. This is accomplished by directly connecting a radio receiver button to the earplug, while a filter ensures the radio audio is received at a reasonable level.
Before any gear is selected, however, employers must get a handle on workplace noise levels, the WorkSafeBC guide notes. It emphasizes that area or spot measurements are not substitutes for personal exposure measures since the first two do not incorporate information about length of exposure.
“Area measurement may either overestimate or underestimate a worker’s noise exposure, leading to inappropriate selection of hearing protection and inaccurate identification of workers who require annual hearing tests.” Employees must not be exposed to an eight-hour average of more than 85 dBA (decibels measured on a meter using an A-weighting filter network).
Once noise levels are determined, steps can be taken to protect hearing. These may involve engineering or administrative controls, such as altering machinery to make it less noisy or limiting the time an employee is exposed to noise. PPE must always be considered the final option.
And remember: hazards exist outside work. “Talking about noise hazards present in everyday activities brings the hearing conservation message ‘home’ in a very meaningful way,” says a release from Howard Leight. “It gets workers’ attention, helps make earplug use habitual, and more often than not gets the neighbours’ attention as well.
Ask a hearing protection professional and he may say the noise reduction rating (NRR) system put out by the Environmental Protection Agency (EPA) appears simple and straightforward, but can prove anything but.
Product packaging may clearly say gear offers 28 decibels (dB) of attenuation. But it would be best not to forget that number needs to be halved (de-rated) when using foam earplugs, and reduced by one-quarter for earmuffs, notes information from the Canadian Centre for Occupational Health and Safety.
“If you bought a car that the [EPA] said got 21 miles to the gallon, but the guy on the lot said to you, ‘don’t forget you have to subtract seven and divide by two’… how much confidence would you have in the miles per gallon rating?” says Jeffrey Goldberg, president of Custom Protect Ear in Surrey, British Columbia.
De-rating has come about because NRR numbers may not live up to real attenuation. “Studies indicate that while some workers in real-world work sites achieve the NRR on the package, many workers do not,” says a release from Howard Leight by Sperian, in Smithfiled, Rhode Island. “This has led to a variety of inappropriate de-rating methods for hearing protectors, and has contributed to much confusion in knowing how to accurately estimate a hearing protector’s attenuation.”
Renee Bessette, marketing manager for the company, says a new NRR system now under development is expected to move from single-number rating to a two-number system. The lower number will suggest the attenuation achieved by an inexperienced, minimally trained hearing protection user; the higher number, for a proficient user.
Brian Myers, portfolio manager for hearing products at 3M Company in Indianapolis, Indiana, says “the problem with the single number is that people think that is exact. People make purchasing decisions every day based on differences of one decibel in an NRR,” Myers says. Fit testing will continue to be required for precise measurements, he emphasizes.
Dan Birch Is Acting Assistant Editor Of OHS CANADA.