Donald F. Groce, Global Glove & Safety Manufacturing, Inc.
Most of us take for granted the enjoyment being able to hear brings to our everyday lives. I enjoy a high-spirited sports event where things get really loud; time with my large, loud family; or visiting the shooting range with my marksman friend. As a huge music fan who loves a concert choir and symphony orchestra, a rock concert or even grand opera, it would be a sad tragedy if my occupational noise exposure affected enjoyment of my favorite activities, because I can no longer hear them as well as I once could.
Hearing loss from occupational noise exposure is lifelong, but is preventable. Not protecting our hearing can be detrimental to the enjoyment of our favorite activities and even our ability to carry on a normal conversation.
The Bureau of Labor Statistics reports hearing loss as the second most common, nonfatal occupational illness, with 19,500 new cases reported in 2015; 69% of these cases were in the manufacturing sector.
The World Health Organization (WHO) quantified and ranked effects of hearing loss in decibels from audiometric testing.
- Normal: (15-25 dB): Can hear and distinguish normal speech regardless of background noise.
- Slight: (26-40 dB): Difficulty hearing soft speech or speech against background noise.
- Moderate: (41-60 dB): Difficulty hearing regular speech even at close distances.
- Severe: (61-80 dB): Can only hear very loud speech or loud sounds such as a fire truck. Hearing aids are needed.
- Profound: No loud speech or hearing aids help. Loud sounds are sensed as vibrations.
According to the Centers for Disease Control and Prevention, 17% of adults aged 20-69 (approximately 40 million) have permanent damage to their hearing from excessive noise. Damage includes hearing loss, tinnitus (ringing in the ears), stress, anxiety and high blood pressure, to name a few. As a preventive measure, CDC recommends limiting exposure to sounds above 100 decibels to less than 15 minutes and sounds above 110 decibels to no more than one minute.
In worst cases, hearing loss even mimics a concussion. Recently, U.S. Diplomats serving in Cuba claimed unverified acoustic sonic attacks, which lasted only a short time, left victims with a myriad of symptoms, including permanent damage to balance and hearing. These attacks are mentioned to emphasize the susceptibility of delicate auditory structures to permanent injury by sound waves.
Noise-induced hearing loss cannot be medically or surgically corrected.
So, Hearing Loss becomes Hearing Lost!
Even one exposure to an extremely loud noise, like a gunshot, explosion or impulse, can cause permanent damage. Prolonged exposure to lower noise levels can be more dangerous than a one-time very loud exposure, because it can go unnoticed.
OSHA has recommended time limits for employee exposure to specific noise levels without hearing protection: Noise levels are measured using a dosimeter by trained safety professionals. Hearing Protection Devices (HPD) are needed after the time limit is exceeded.
|of Noise||Time Limit||OSHA Recommendation|
|< 85 dB||>8 hours||No hearing protection device required|
|>85 dB||Action Level||Hearing protection device required|
|92 dB||<6 hours Decibels||After 6 hours, HPD required|
|95 dB||<4 hours||After 4 hours, HPD required|
|97 dB||<3 hours||After 3 hours, HPD required|
|100 dB||<2 hours||After 2 hours, HPD required|
|102 dB||<1.5 hours||After 1.5 hours, HPD required|
|105 dB||<1 hour||After 1 hour, HPD required|
|110 dB||<30 minutes||After 30 minutes, HPD required|
|115 dB||<15 minutes||After 15 minutes, HPD required|
OSHA recommends the following Hearing Protection measures:
- Eliminate the noise when possible.
- Engineering controls, like noise absorbing panels; modernize or containment of machinery in soundproof room.
- Isolate workers from the noise.
- Set exposure time limits.
- Wear hearing protection devices when necessary.
Earplugs and earmuffs are very effective hearing protection devices that lower but do not completely shut out the sound. Alarms or warnings can still be heard, and communication is still possible. The attenuated sound is not loud enough to cause damage.
Earplugs, available in disposable versions with straps, represent an extremely inexpensive way to provide hearing protection in many occupational situations.
Earmuffs fit over the entire ear. Some are equipped with microphones and speakers to enable worker communication.
Like gloves, hard hats or any safety device, earplugs and ear muffs can be tremendously helpful, but only if they are used properly.
OSHA mandates that noise levels be measured. Employers are required to notify employees of the risks, must provide hearing protection and must train employees on proper use of hearing protection devices.
Gradual hearing loss can go undetected. Employees should undergo audiometric testing annually to assess whether hearing loss is occurring. Immediate action is required if hearing loss is detected.
Hearing protection devices must have a Noise Reduction Rating (NRR). This rating was developed by the Environmental Protection Agency (EPA) to measure their protective ability. The identified noise source is brought down to a safer level or attenuation by wearing a hearing protection device.
Hearing Protection Devices, such as earplugs or ear muffs, reduce harmful noise levels in some situations but not in all. OSHA says you cannot determine the adjusted noise level by simply subtracting laboratory derived noise reduction ratings from environmental noise levels measured by a dosimeter. Laboratory derived NRR is seldom met in industrial settings. OSHA recommends subtracting a correction factor of seven dB from the NRR.
OSHA also recommends applying an additional 50% reduction in the NRR because of fit limitations.
Although some experts say that addition of earmuffs over earplugs adds 10-15 dB more of noise reduction, OSHA says that adding a second hearing protection device reduces the overall noise attenuation by only five additional decibels. The combined attenuation of more than one hearing protection device is not as beneficial as you would think.
The table shown below lists typical noise measurements from every day and occupational situations. The attenuated protection offered by earplugs with a 33 Noise Reduction Rating is shown. The last column shows the attenuation adjusted for wearing both earplugs and earmuffs.
|Noise Producing Environment||Typical Sound Level (Decibels)||Hearing Protection Device Earplugs (Noise Reduction Rating)||OSHA Correction Factor (-7 dB) with 50% Reduction||Hearing Protection Device Attenuation (Earplugs Only)||Hearing Protection Device Attenuation (Earplugs with Earmuffs)|
|1. Boiler Room||90||33||13||77||72|
|2. Truck Traffic||90||33||13||77||72|
|4. Construction Site||100||33||13||87||82|
|5. Chain Saw||100||33||13||87||82|
|6. Pneumatic Drill||100||33||13||87||82|
|7. Symphony Concert||110||33||13||97||92|
|8. Power Saw||110||33||13||97||92|
|9. Baby Crying||110||33||13||97||92|
|10. Sand Blasting||115||33||13||102||97|
|11. Football Game||117||33||13||104||99|
|12. Heavy Equipment||120||33||13||107||102|
|13. Jet Engine||120||33||13||107||102|
|14. Jack Hammer||130||33||13||117||112|
|15. Percussion Section at Symphony||130||33||13||117||112|
|16. Fire Arms||140||33||13||127||122|
|17. Rock Concert (loudest)||150||33||13||137||132|
For noise producing environments listed above, HPDs should be worn in all the yellow highlighted activities.
Surprisingly, even with earplugs, exposure to a symphony concert, power saw or baby crying should be limited to no more than 3 hours. For sand-blasting, hearing damage can occur if you are exposed longer than 15 minutes. Wearing earplugs raises the exposure time to 1.5 hours, and wearing earplugs and earmuffs raises the exposure time to 3 hours.
For heavy equipment or jet engine noise, you can only be exposed for one minute without a hearing protection device, for up to one hour with earplugs and for up to 1.5 hours with earplugs and ear muffs combined.
Your safety equipment supplier can answer additional questions on how to maintain your healthy level of hearing by protecting your ears from environments with dangerous levels of occupational noise. WMHS