There are many ways workers learn how to wear earplugs - in safety briefings, group training sessions or in an introduction to a job site. Too often, the person providing hearing protector training is little more than a dispenser, handing the worker earplugs and saying, “Here, use these around loud noise” or “Stick these in your ears.”
However, numerous studies have shown that the best way for workers to learn about hearing protection is through one-on-one training. Workers need to know not only when and why they should use earplugs, but how to use them effectively. This article will focus on what trainers need to know to teach workers how to use earplugs effectively.
Figure 1 shows the difference in attenuation between two fittings of the same earplug in the same worker's ear on the same day. In both cases, the earplug appeared to be far enough in the ear canal to satisfy a cursory compliance check. But the difference is that a good insertion - i.e., when the earplug is deeply inserted and achieves a good seal in the ear - is enough to cause a 30+ dB improvement in attenuation. The worker with a bad fit may be lulled into a false sense of protection when he detects slight muffling of high-frequency sounds or when some of the “edge” is taken off shrill noise. But because the poor fit has seriously compromised low-frequency protection, the effective overall protection is 0 dB!
Training any new skill - whether it's how to use a tool or how to be safe on the job - can be done by presentation or lecture, hands-on training, small group training, consulting from a distance, informal training or one-on-one training. Studies of the effectiveness of earplugs to block noise reveal that one-on-one training is the most effective method to get a worker to use hearing protection appropriately. One study showed one-on-one training for individuals with very poor attenuation resulted in an average 14 dB improvement in attenuation. (From “Hearing Protector Attenuation Measurement on the End-User,” by Kevin Michaels and Cindy Bloyer.)
Achieving good earplug fit is not always easy, and there are several points trainers need to understand in order to use that one-on-one training time well. First, there are three steps to fitting an earplug: 1) preparing the earplug (for roll-down or foam plugs); 2) opening the ear canal; and 3) inserting the earplug. Let's look at each of these steps individually.
PREPARE THE EARPLUG
No-roll foam and multiple-use earplugs do not require much preparation, but a very critical part of getting adequate protection with foam earplugs is the roll-down. With clean hands, roll the entire earplug into the narrowest possible crease-free cylinder. Most instructions show rolling with the fingers of one hand, but I like to use two hands for a really tight cylinder.
When rolled down well, the earplug should be a little longer and noticeably stiffer. This allows the earplug to work its way around the first bend of the ear canal. To demonstrate this in one-on-one training, roll a foam earplug down very tightly and push it against one finger so that it glances off the finger and slides past. Once the earplug is rolled very tightly, whether you use two hands or one, move it quickly to the ear canal for placement.
OPEN THE EAR CANAL
For all types of earplugs, the more open the ear canal, the easier it is to insert the earplug and achieve a proper fit. To open the ear canal, simply reach over your head and pull on the top of your ear. Usually, pulling up and back opens the canal best. However some ear canals open more fully by pulling out on the ear.
There are a couple of methods to help users learn the best way to pull their ear open in one-on-one training. One is to look at the person's ear canal (be sure to look at both ears as they may be different) and give them feedback as to when the canal is most open. Another way is to take a picture of their ear canal at rest and then again as they reach over and open their canal. Many phones have cameras so it's easy to get a digital photograph and then just delete it.
Figure 2 shows an ear canal before is has been opened. Notice that the first bend in the ear canal is very near the opening, so that as soon as an earplug is inserted it will run into the wall of the canal. Figure 3 shows the open ear canal. Notice that there is now space to insert the earplug more easily around the canal wall at the bend.
INSERT THE EARPLUG
The earplug must be inserted well inside the ear canal to be effective. Once a roll-down foam earplug is prepared, quick insertion is a key to getting adequate attenuation. Stopping to admire the great job you've done with the roll-down is not a good idea!
Opening the ear canal properly makes insertion of the earplug much easier. A properly rolled foam earplug should basically lie on the ear canal floor and expand to seal the entire canal. Whether using single-use or multiple-use earplugs, a little movement or wiggle often is required to place the earplug in the correct location, well inside the ear canal.
Earplugs that are placed too near the entry to the ear canal are not as effective and can cause what's known as the Occlusion Effect. The Occlusion Effect is the amplification of body-borne sounds caused when you occlude or close off the ear canal. This can be demonstrated by singing the vowel sound “ee” while you lightly push on your tragus - that little flap at the opening of your ear canal. Most people hear the “ee” become much louder with their ear occluded. With hearing protectors, the Occlusion Effect is reduced by inserting the earplug deeper into the ear canal, or by stiffening the soft portion of the ear canal by using an earplug with more surface contact in the ear canal.
CHECKING THE FIT
There are several ways of verifying whether the earplug is properly fitted:
Visual Check — For earplugs with a stem (a firm protruding piece intended to be grasped by the user for insertion), only the tip of the stem should be visible to someone looking at you from the front, or when you view yourself in a mirror. All flanges of a flanged-earplug should be well inside the ear canal. For earplugs without stems, the ends of the earplugs should not be visible to someone looking at you from the front. An earplug that clearly is visible from the front is a warning sign of poor insertion.
Acoustic Check — A hearing protector only is useful when it achieves an acoustic seal in the ear canal. An acoustic seal causes a very pronounced lowering of noise levels. Here is one way of checking the acoustic seal of an earplug. With earplugs inserted, cup your hands firmly over the ears and release. The earplugs should be blocking enough noise so that covering the ears with your hands results in no significant change in noise level.
Subjective Fit Testing — Several new tools now allow accurate measurement of real-world attenuation, so that workers (and employers) can verify the protection offered by earplugs. One such system uses a method in which a probe microphone is inserted into specially modified earplugs. Users don these test earplugs and listen while a loud noise sample is played. Software then calculates how much noise is blocked by the earplug. Another system administers a short listening test to the users, both with/without earplugs inserted, and calculates real-world attenuation from the difference in the two tests. This system can be used with any earplug model (no modification required).
In recent field attenuation studies of hearing protectors using these new fit testing systems, workers who consistently failed to achieve good fit and attenuation results with one earplug often showed significant improvement simply by switching to another earplug type or style. Workers who tried a second pair of earplugs - even with no additional training - often had major leaps in attenuation, bringing them closer to the rated attenuation for that earplug.
This confirms the wisdom in OSHA's requirement to offer a “variety of suitable hearing protectors” to noise-exposed workers. Some workers simply will never achieve satisfactory attenuation with one particular model of earplug. And if that earplug is the only choice offered at the worksite, some workers are destined for perpetual under-protection. Offering a second choice of suitable earplugs and earmuffs significantly improves the probability of more workers obtaining adequate protection.
A personal, one-on-one approach to training has been shown to increase the effective fit of earplugs. Offering a variety of earplugs, as well as including subjective fit testing with the worker's own earplugs, can increase hearing protection compliance and reduce the incidence of noise-induced hearing loss on the job.
Dr. Theresa Y. Schulz, Lt. Col., USAF (ret), recently joined Sperian Hearing Protection LLC as hearing conservation manager. She began her career as an audiologist in the military and since her retirement in 2004, has worked in a number of positions, including team leader of the Hearing Loss Prevention Branch at NIOSH. She is a certified professional supervisor for audiometric monitoring (CPS/A), immediate past president of the National Hearing Conservation Association, a certified member of the American Speech-Language-Hearing Association and a fellow in the American Academy of Audiology.