Warning: Hearing Loss becomes Hearing Lost

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:

  1. Eliminate the noise when possible.
  2. Engineering controls, like noise absorbing panels; modernize or containment of machinery in soundproof room.
  3. Isolate workers from the noise.
  4. Set exposure time limits.
  5. 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
3.      Lawnmower 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