This presentation on Hearing Conservation is adapted for the U.S. market. It is divided into eight chapters: - Noise and Acoustics - How We Hear - OSHA Standard - Regulatory Groups - Hearing Protector Selection - Evaluating Noise Reduction - Fitting Tips - Hearing Protector Use and Care In its entirety, it requires up to two hours to present all material in depth. But chapters can be deleted or added as needed to adapt to the needs of the audience.
Noise damage can occur on-the-job as well as off-the-job (loud music, shooting, power tools, crowd noise). Good hearing conservation should be practiced, no matter what the setting.
Noise damage is different from most other occupational injuries. It causes no pain or visible trauma (the ears do not bleed when hearing is being damaged), it leaves no visible scars, it is unnoticeable in its earliest stages (workers with noise-induced hearing loss often do not even notice themselves that they are losing hearing until it is too late), it accumulates with each over-exposure, and it generally takes years to diagnose. (<Space> to add bottom line message) But Noise-Induced Hearing Loss (NIHL) is permanent and 100% preventable.
Typical noise levels on-the-job and off-the-job … a lawnmower at 94 dB, heavy equipment at 100 dB a rock concert at 120 dB. Unprotected exposures at these levels can cause damage. According to OSHA regulations, no exposures of any duration are allowed over 115 dB.
Here is a good rule of thumb to use in determining whether background noise is 85 dB or higher: If you must shout to be understood by somebody about one meter away, that background noise is hazardous.
Exposure limits in noise exposure are a trade-off between sound level (measured in decibels) and duration of exposure (time). For an 8-hour exposure, for example, the maximum permissible sound level is 90 dB. Anything beyond 8 hours at this noise level is not allowed.
But for higher exposure levels, such as 95 dB, the maximum allowed exposure time is only 4 hours. In a time-weighted average (TWA), higher noise levels allow shorter exposure times, and lower noise levels allow longer exposure times.
(Animation should play automatically if animation file LjudTillNerv is in same folder as PPt file.) This animation shows how we hear. Sound waves enter the ear canal and cause the eardrum to vibrate. Bones behind the eardrum transmit these vibrations to the cochlea – the snail-shaped organ where the nerves of hearing are located. Receptor cells in the cochlea convert these vibrations into electrical impulses, and send them to the brain, where we interpret these impulses as sound. When noise damages hearing, it does not damage the eardrum or bones (unless it is a loud blast or explosion). Generally, loud noise damages the receptor cells in the cochlea, and these nerve cells are irreplaceable – they do not grow back like a fingernail.
(<Click> on drawing to play animation and tone sweep. The animation and tone sweep will play if the TonPlats file is in the same folder as the PPt file.) The animation shows how the cochlea is tuned in different areas to respond to different tones. The base of the cochlea is sensitive to high frequency sounds -- it is this part of the cochlea that is damaged when loud noise enters the ear. It makes little difference whether the incoming sound is high-frequency or low-frequency – ANY loud noise will cause a high-frequency hearing loss, because the region of the cochlea hit hardest by incoming sound waves is the region where the high-frequency receptor cells are located.
Here, we show actual magnified photos of the human cochlea with various stages of damage: - The magnified photo of a cochlea from a 17 year-old girl shows nerves and receptor cells still intact (indicated by the dark areas in the first turn of the cochlea.) - The second photo of a 76 year-old shows fewer receptor cells due to aging (some white gaps in the receptor cells), but still intact. - The third photo of a 59 year-old noise exposed man shows significant destruction of the receptor cells. This third photo shows that noise damages hearing much more than aging alone, and much faster.
In speech and conversation, these are the sounds that are first affected by a noise-induced hearing loss --- they will be muffled, compared to other sounds of speech.
Noise reduction is only one of many factors in determining the best hearing protector for a noise-exposed worker. The ideal hearing protector is simply the one that the worker will wear 100% of the time for hazardous noise exposures. Depending on the workplace, there are many factors that may go into that decision: - Comfort - Noise Reduction - Size - Communication Needs - Special Job Requirements - Cleanliness - Compatibility with Other Personal Protective Equipment
This slide can be used to address common worker complaints about hearing protectors, with the following responses: - Even if you have lost some hearing, it is critical to prevent further hearing loss by wearing HPDs. - The ear cannot ‘get accustomed to noise’. Instead, this may be a sign of a mild hearing loss developing. - If uncomfortable, find an HPD style that is more comfortable for extended wear. A properly-fit HPD should feel comfortable for all-day use. - Earplugs are designed to insert at a safe distance from the eardrum. You will not damage eardrum by hearing HPDs. - An earplug does not cause ear infections, but it may aggravate an existing ear infection. If you suffer from a current ear infection, switch temporarily to earmuffs until the infection heals. - Users of HPDs will hear sounds differently (co-workers’ voices, machinery, etc.). But HPDs reduce the background noise level as well as the signals you want to hear. It may require some adjustment period, but most users find they can still hear the signals they want to hear, even while wearing HPDs. - Hearing aids are no substitute for normal hearing, and HPDs should be worn to prevent hearing loss.
Users with unusually small or large ear canals need to experiment with earplugs to find the size that provides a clear acoustic seal. However, one study found that two-thirds of users erred on the side of choosing earplugs that were too small. Choose the correct size that makes a good acoustic seal.
For earplugs, effective protection is dependent upon a deep insertions. With foam earplugs, this is accomplished by following these three steps: - Roll down the foam earplug to a small crease-free cylinder - Straighten out the bend in the ear canal by reaching over the head with the free hand, and pulling the ear up and out. - Insert the earplug well into the ear canal and hold it in place a few seconds while the foam fully expands
(Click to play this training video showing proper insertion of foam earplug.)
How do we know if the earplug is in far enough? When properly fitted, the end of the earplug should not extend beyond the tragus (the flap at the opening of the ear canal). When viewed directly from the front, a properly-fit earplug should not be visible.
(Click to show this training video, demonstrating that a properly fit foam earplug is not visible when viewed from the font.)
Steps for proper insertion of no-roll foam earplugs. (see Howard Leight fitting poster, available free of charge)
Steps for proper insertion of multiple-use earplugs. (see Howard Leight fitting poster, available free of charge)
There are two ways to determine if the earplug is in far enough to provide adequate protection: 1) Visual Check. When viewed directly from the front, the end of a properly-fit earplug should not be visible. 2) Acoustic Check. Cup your hands tightly and place them over your ears, then release. When earplugs are properly fit and doing their job, there should be no noticeable change in the noise level. If the earplugs are not inserted far enough, there will be a noticeable change in the noise when hands are cupped over the ear.
Proper fitting of earmuffs.
The best earmuff fit is only obtained when there is a proper seal around the pinna (the outer ear). Remove hair or other obstructions that may interfere with a good seal between the earcup cushion and the head.
Hearing product group summary.
Advantages / disadvantages of earplugs.
Use and care of earplugs.
Advantages / disadvantages of banded hearing protectors.
NOISE AND ACOUSTICS How do I know if the noise levels are hazardous? If you must shout to be understood over the background noise when standing about one arm-length away from somebody, that background noise is hazardous.
NOISE AND ACOUSTICS Time-Weighted Average Permissible Exposure Limits
OSHA STANDARD Time-Weighted Average Permissible Exposure Limits
HPD SELECTION The Best Hearing Protection COMPATIBILITY WITH OTHER PPE COMPATIBILITY WITH OTHER PPE COMFORT COMFORT NOISE REDUCTION NOISE REDUCTION SIZE SIZE COMMUNICATION NEEDS COMMUNICATION NEEDS SPECIAL JOB REQUIREMENTS SPECIAL JOB REQUIREMENTS CLEANLINESS CLEANLINESS
HPD SELECTION Common Objections to Wearing HPDs “ Hearing protectors are uncomfortable.” “ I don’t need them, I am used to the noise.” “ I already lost some of my hearing, so why should I wear them?” “ I can’t hear my co-workers if I wear them.” “ I can always get a hearing aid.” “ Can I hurt my eardrums if I insert a plug to deeply.” “ My machine sounds different.” “ Won’t I get an ear infection?”
FITTING TIPS Find the Right Size Maximum protection is only accomplished when an earplug acoustically seals in the ear canal. No earplug fits all ear canals, so manufacturers have responded with a variety of sizes. It is important to find your right size to obtain an acoustic seal
FITTING TIPS ROLL-DOWN FOAM 2. Pull Back pinna by reaching over head with free hand, gently pull top of ear up and out 1. Roll entire earplug into a crease-free cylinder 3. Insert earplug well into ear canal and hold until it fully expands
Reach over head with free hand, pull ear up and back and insert earplug well inside ear canal.
2. Earplugs should be inserted as shown in these drawings. Stop pushing earplug when finger touches the ear. 3. If properly fitted, the end of the earplugs should not be visible to someone looking at you from the front.