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What’s New with Earplugs?
By Lee D. Hager - Sonomax Hearing Healthcare, Inc.
March 2005
Regardless of our best efforts to manage and control noise, people go to work every day in jobs or tasks that entail enough noise to put their hearing at risk. Until the battle of noise control is decisively won, making every workplace everywhere free of hazardous noise, hearing protection devices (HPD) will have a key role in any comprehensive hearing loss prevention program.
The challenge is to find ways to select and use HPD more effectively. Noise-exposed workers have been using HPD since the late 1960’s, but hearing loss has continued to build. Some key issues have recently been identified that can help explain this phenomenon.
The Key Issues
Most HPD commercially available today was designed in the 1960’s and 1970’s with comfort as a last consideration – but discomfort is the number one reason HPD users say they take their HPD out, even in high noise areas. Design goals were maximum attenuation, ease of manufacturing, and cost – all important issues, but none as important as user comfort, if our intent is to protect hearing.
Many types of HPD in use today require manipulation or preparation before use. Foam earplug instructions, for example, indicate that these devices should be rolled between the thumb and forefinger into “tight, crease-free cylinders”, and be inserted to the ear while the opposite hand reaches up and over the head to pull the pinna up and away from the head to open and straighten the ear canal. Today’s aging workforce with bursitis in the shoulder and arthritis in the knuckles has a hard time engaging in this process. It is no wonder that the earplugs are used wrong, as poor ergonomic design can make it difficult to use them correctly.
Performance is another key issue. Due in part to the ergonomic and comfort issues stated above, and in part to individual variability, the noise reduction rating or NRR listed on each package of HPD has little relationship to the amount of protection actually provided by the devices in use in the field. NIOSH, in their 1998 Criteria Document, indicated that manufacturers overstate field performance of some devices by 140% to as much as 2000% Some pundits go so far as to sarcastically state that NRR does not really mean noise reduction rating – what it really means is “not really relevant”!
And what if HPD actually performed to their laboratory standard? NIOSH indicates that 90% of industrial noise exposures in the US are less than 95 dBA, meaning that the vast majority of users need a reliable 12 to 15 decibels of protection. What’s needed is not higher and higher attenuation – it is instead devices that, when used properly, provide an consistent and appropriate amount of protection. NRR of 29 is meaningless when what is needed is a dependable14 dB of real protection. Even in relatively noisy environments, people need to use their ears on the job – and they find a way to do that, even if it means pulling the earplug halfway out and compromising the performance of the HPD intended to protect them from noise.
The testing procedures in use today were developed in the late 1960’s and early 1970’s. They assume that there is no feasible way to test HPD performance on individuals, and base the NRR on statistical manipulation of laboratory tests. New technologies, though, have introduced ways to conduct individual HPD performance validation, much like the quantitative fit test for respirators.
Ergonomics and Comfort
While there is still no way to provide a quantitative test of comfort for HPD, several manufacturers have introduced products that lead down a trail of comfort and ergonomics.
E•A•R has introduced several variations of their famous yellow foam with insertion handles. The Express Pod™ and Gripper™ are both far easier to insert than the Classic™, do not require the “roll-down”, and may not require the over-the-head pinna pull for proper insertion.
Howard Leight has introduced an earplug called the Matrix™. It is a multi-sized, no-roll foam earplug that achieves acoustic seal by reaching and filling the first bend in the ear canal.
In addition, several manufacturers have adopted versions of expandable foam earplugs fabricated from polyvinyl rather than polyurethane. The polyvinyl plugs, like the Howard Leight Max™ and E•A•R Ultrafit™ tend to be softer. They may be harder to insert initially due to their flexibility, but they can be more comfortable for long-term use once they are in place.
Communication and Moderate/Low/Flat Attenuation
The E•A•R UltraTech™ and Bilsom NST™ series are both designed to provide moderate attenuation, in the range of 12 to 17 dB. Additionally, these devices are designed to provide a relatively flat frequency response, thus proving a more “natural” sound.
While these efforts help the passive HPD user greatly, other manufacturers have introduced electronics interfaces to their devices. Sonomax™ has developed a systems-based approach that includes an instant-delivery, custom-fit earplug with attenuation adjustments to match the noise exposure of individuals along with a radio communication interface. The HPD becomes the custom-fit radio earpiece. David Clark manufactures a full line of combination HPD and radio units in earmuff form, and Peltor and others are starting to bring this interface to their lines.
Electronics
The world of electronics holds some promise for HPD users as well. Sound restoration technology incorporates earmuffs with microphones mounted on the outside, and electronics on the inside that bring quiet sounds up and loud sounds down to about the same safe level. When shopping for these devices, make sure to get stereo (one microphone for each ear) units that are UL listed. Knock-offs are available from importers, but buyer beware.
Peltor has introduced a modification to the sound restoration technology called push-to-listen, or PTL. On these units, the “pass through” technology is engaged by pushing a button on the earmuff, with an automatic timed shutoff. This is intended for those who need to hear specific things on the job, but who don’t want to hear everything.
The promise of active noise cancellation is alive for earmuffs. This technology involves fairly sophisticated computer electronics that look at the noise outside the earmuff, and generate “anti-noise” to cancel out offending sounds. The good news is that it works wonders, as evidenced by the Bose Sanctuary™, Sony™, and other devices offered for sale in the Sunday paper and in the airline magazines. The bad news is that they are not the HPD of choice in industry. Cancellation technology today works best at low frequencies, like those generated by HVAC units or jet engines. Most industrial noise contains enough high frequency content that the cancellation technology will have little effect – meaning that strictly in terms of protection from noise, a passive earmuff will probably work nearly as well for less than one-tenth the price.
One problem with most electronic devices is weight. Sound restoration, noise cancellation, and other electronic HPD require power, meaning typically at least one 9 volt battery. The combination of electronics, power source, and earmuff can be heavy and uncomfortable, especially in hot or humid environments.
Real-world Testing
The testing processes for HPD have been unchanged for over 25 years. Under current EPA rules, a test panel of 10 subjects takes a hearing test, with and without HPD in place. The difference, taking a bit of statistical massage into account, indicates the NRR.
The challenge is that the lab environment is not the workplace. There is no supervisor yelling, no hot and steamy environment, and the HPD are put in place by technicians trained to get the maximum attenuation from the devices.
New approaches may change the way we look at HPD protection values. FitCheck™ is a process that permits a personal attenuation test on earplugs. The test is fairly simple to administer and can provide a great deal of information about how people use HPD. The Sonomax Solution™, described above, also includes an individual quantitative fit test of each set of customs earplugs are part of the fitting process. Building records of individual fit testing is a viable defense to hearing loss worker compensation and recordability claims.
What Does the Future Hold?
Several interesting things are on the horizon for HPD users and manufacturers. The US Environmental Protection Agency, which is responsible for the government rules covering HPD evaluation and labeling, is in the process of revising their regulation. The last time this process was undertaken was in the early 1980’s, and the rule cites standards as old as 1974. Progress continues as EPA undertakes the painstaking process of rule revision.
Inroads being made by some new players in the HPD field are forcing old-line manufacturer to revisit their offerings. Peltor, for example, has introduced a new line of polyvinyl earplugs in pink and green to appeal to a younger demographic. Bilsom is featuring a range of options in their earmuff selection that was unheard of five years ago, from “noise blocking” to “sound management” (referred to here as sound restoration) to communication to radio/personal entertainment units. The industry is becoming increasingly responsive to the varying needs of the changing workforce – and so much the better for the HPD user! HPD Links
Mr. Hager is a Hearing Loss Prevention Consultant with Sonomax Hearing Healthcare Inc. He can be contacted at 517-647-5882 and at lhager@sonomax.com.
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Copyright © 2006
Phase To, Inc.
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