Sound can be transformed into the unsound when excessive: too much noise, too much vibration, even too much exposure to solvents can lead to hearing loss that no amount of second-guessing will restore. A whole host of controls should be considered to protect workers from noise-induced hearing loss (NIHL), but the two main categories of personal protective equipment (PPE) to achieve this are earplugs and earmuffs.
Perhaps the strangest thing about protective gear is that the ultimate goal is that it be rendered unnecessary. Until that time, it may be best to take the conservative approach to hearing conservation.
A hearing-protection program has a number of essential elements: noise exposure assessment/monitoring; education/training/motivation; engineering and administrative controls; hearing-protector devices; audiometric testing; record keeping; and program evaluation.
Conservation has long been a song sung by the choir. “If prescriptions for eyewear are important for workers to see properly to preserve their vision, then it makes sense for workers to take care of their hearing the same way,” says Brad Davidson, founder of HearSafe Canada in Mississauga, Ontario.
But is this buy-in resulting in on-the-floor protection? Many employers today explore engineering and administrative-control options first and elect hearing protection if those options do not lower the noise below hazardous levels.
Theresa Schulz, Ph.D., hearing-conservation manager for Howard Leight Hearing Protection in Smithfield, Rhode Island, notes that peer-reviewed studies and research data show that workers are more motivated to use PPE consistently when noises are louder than 90 to 95 decibels (dB). At lower levels, Dr. Schulz says, “the noise is still hazardous, but not as annoying, and workers can be lulled into thinking they don’t have to use PPE.”
That false security is of concern, since workers exposed to noise in the 80 to 90 dB range can develop NIHL. “It can be tempting to gloss over engineering and administrative controls and see PPE as the answer,” she cautions.
If protective gear is needed, working conditions will certainly have some influence on product selection. But choices — particularly as they relate to comfort, fit and practicality — can get downright personal, notes information from the Canadian Centre for Occupational Health and Safety (CCOHS) in Hamilton, Ontario.
Earmuffs and earplugs each offer their own level of attenuation and protection. Some things to bear in mind when determining which option is best for a workplace include the following:
— workers generally prefer earplugs in hot environments;
— banded earplugs are a good choice for intermittent, low-noise environments; and
— communications headsets offer protection while allowing workers to communicate in high-noise environments.
Compliance is a healthy sign of a conservation approach, but compliance without proper fit can nullify benefits.
Fit to protect
Dr. Schulz says that “a poorly fit hearing protector can be uncomfortable, can let in too much hazardous noise or can overprotect, blocking too much noise and creating other safety issues.” To fit earmuffs, the main considerations are correct size and donning method, while earplug fitting may be trickier. “Earplug fitting is much more variable between workers, between different earplugs and even one worker fitting and refitting the same earplug repeatedly,” she cautions.
Gear must be worn at all times during noisy work; otherwise, protection drops off dramatically. Australian-based ProChoice Safety Gear notes that “a hearing protector that gives an average of 30 dB of noise reduction if worn continuously during an eight-hour workday becomes equivalent to only nine dB of protection if taken off for one hour in that noise.”
CCOHS also offers some examples of the maximum protection provided for the percentage of time used: 50 per cent, three dB; 60 per cent, four dB; 70 per cent, five dB; 80 per cent, seven dB; 90 per cent, 10 dB; 95 per cent, 13 dB; 99 per cent, 20 dB; and 99.9 per cent, 30 dB.
Whatever part of the body equipment is meant to protect — eyes, feet, hands or ears — comfort is a critical part of the equation. HearSafe Canada reports that a lack of comfort and difficulty with properly inserting an earplug can bring with it a lack of compliance. And equipment that is not used cannot protect.
The company cautions that disposable earplugs may come with a risk that they will either over- or under-protect. While the work-related hazards around under-protection are clear, it notes, over-protection can result in gear being removed repeatedly.
For maximum comfort and protection, HearSafe Canada notes there is no better option than custom-made gear. By taking an impression of the ear canal, the plug will be custom contoured. Fit tests and proper filtration must also be part of the mix, Davidson says.
Rate it tops
When a worker remains in one noisy location for much of his day, the need for hearing protection is an easy call. But what if noise exposure is intermittent and levels are varied? Any information can be helpful, although one proviso is that users must understand what the information means.
Noise ratings are not a measure of the protection received by the user, Dr. Schulz explains. “Noise ratings are measured to show what that protector can provide, not what it does provide,” she advises.
CCOHS cites information from the National Institute for Occupational Safety and Health in the United States. If fit data are not available, NIOSH recommends de-rating hearing protectors by a factor that corresponds to the available real-world data. For earmuffs, subtract 25 per cent from the manufacturer’s labelled NRR; for formable earplugs, subtract 50 per cent; and for all other earplugs, subtract 70 per cent, the agency notes.
Carefully weighing factors when selecting equipment, clearly, is the smart thing to do. But some equipment itself is getting downright intelligent. Intelligent hearing protection includes electronic earmuffs, which amplify quiet sounds, but still protect against impulsive noise, according to Dr. Schulz.
Dr. Schulz points to a number of innovations in hearing protection. For hearing-impaired workers, electronic earmuffs will amplify ambient sounds. When a hazardous level is reached, she says, “the amplification cuts off and the muff is now a passive earmuff.”
Some products combine the high performance of a passive earmuff with advanced electronics. Workers are able to clearly hear low-level sounds, but if dangerous noises occur, the electronics limit the noise. These tactical products provide protection in high-noise environments, and models are also available to interface with two-way radios.
Active noise reduction could provide a solution for workers whose exposures are fairly constant, low-frequency hazardous noise. Available with both earmuffs and earplugs, Dr. Schulz explains, the technology includes “a microphone that analyzes the incoming noise, turns it 180 degrees out of phase and rebroadcasts it into the ear canal so that the sound waves are acoustically cancelled.”
BKK Enterprises in Dryden, Ontario distributes ZEM hearing protection, which uses a patented technology for sound cancellation. The technology is well-suited for damaging noise environments, such as manufacturing, utility work, construction, landscaping, airlines and woodworking.
Sonically sealed chambers form a vacuum that pulls harmful sounds away from the sensitive ear anatomy, the company notes. It reduces low-frequency noise, the noise that masks speech and important sounds or alerts.
There is also a trend to offer products that appeal to workers who will make up the work force of tomorrow. For example, there are headsets for people who want hearing protection while listening to the radio or an MP3 player. These limit the audio output to 82 dB plus offer a CSA Class A rating or an NRR of 26 dB.
CCOHS recommends that employers provide workers a choice of gear — as long as it can do the job — to ensure hearing is protected and worker acceptance maximized.
Angela Stelmakowich is a former editor of OHS Canada.