comply with OSHA occupational noise exposure standards, companies are required
to limit the amount of noise any one worker is exposed to on the job. For most
applications, a single layer of hearing protection will be sufficient. However,
double hearing protection may be necessary under certain conditions.
When is Double Hearing Protection Required?
first step is to know the noise levels your employees encounter each day. Workplace noise
are dependent on the specifics of your workplace. Generally, an employee will
wear a dosimeter during their shift. The dosimeter measures noise exposure and
if you find workers are exposed to an average above 85 decibels (dB) over eight
hours, then double hearing protection may be useful along with a required hearing conservation
in an environment above 100 dB, OSHA rules encourage the use of double hearing
protection. Some industry specific requirements have a lower standard,
requiring double protection above 105 dBa, but OSHA’s guidelines are safest. To
comply with all regulations, it best to provide double hearing protection when
workplace noise levels exceed 100 dBa in an 8 hour weighted average.
Hearing Protection provides a 4 to 8 dB boost, on top of the normal parameters
of the ear muffs, for example. Providing ear plugs with ear muffs can reduce
noise an additional 85% which leads to a significant reduction in noise-related
injuries. The most common form of double hearing protection is the use of ear
plugs with ear muffs.
Do Your Workers Have Enough Hearing Protection?
any noise reduction device (earplugs, ear muffs), a Noise Reduction Rating
(NRR) is provided. Peltor Optime 105
Headband Ear Muffs, for example, have an NRR rating of 30.
determine how NRR rating affect dB, take the NRR number subtract 7 and divide
that number by 2.
our example: (30 – 7) / 2 = 11.5
worker wearing Peltor Ear Muffs with a 30 NRR will experience an 11.5 dBa
reduction in noise. If your workers are exposed to 100 dBa, then with the
earmuffs they will be exposed to 88.5 dBa.
your workplace requires more, then double protection through 3M Classic Ear Plugs will provide an additional 5 dB of
protection. By themselves, 3M earplugs have an NRR rating of 29, but when
doubled with Peltor Ear Muffs, an additional 5 dB is added to the highest rating.
a workplace with an 8 hour average of 100 dB, let us look at a worker wearing
both 3M Ear Plugs and Peltor Ear Muffs:
Peltor Ear Muffs: 30 NRR
3M Ear Plugs: 29 NRR
Double Protection: +5 NRR
Total Protection: 35 NRR
let’s calculate the dB reduction of our dual protected worker with 35 NRR.
reduction = (35 – 7) / 2 = 14
worker in a setting with 100 dB with dual protection will now experience 86 dB
over eight hours. This dual protection complies with OSHA’s regulations. Both
you and your workers are protected.
Special Cases: When OSHA Requires More Protection
most workspaces, noise must be below 90 dB over eight hours. However, if your
worker experienced STS hearing loss, then more is necessary. To
determine if your employee suffered a Standard Threshold Shift (STS), answer 3
- Has your employee suffered a 10dB loss in one or both ears?
- Is your employee’s overall hearing level at 25dB?
- Is your employees hearing loss work-related?
- Under OSHA Guidelines, hearing loss cases assume that the loss occurred at work. The burden of proof lies with employers to prove otherwise.
- Hearing loss aggravated by a work environment classifies as work-related hearing loss.
If you answered yes to each question above then more hearing protection is required for that employee. An additional 5 dB of protection will put you in compliance and protect your employees from further hearing loss. What Noise Exposure is Ideal?
as too little noise exposure is dangerous, so too is the opposite. Excessive
noise reduction can cause accidents related to an inability to hear colleagues,
alarms, and a general lack of awareness. If a worker needs to remove hearing
protection to listen to their equipment or converse with a colleague, then
hearing protection may be excessive.
aim to reduce noise to bring exposure down to 75 – 85 dB. The CDC recommends
that a single layer of ear protection be used for workplaces with noise levels
below 100 dB. Above 100 dB, a dual protection layer may be required to reach
the ideal workplace noise
Should You Use Ear Plugs or Ear Muffs?
quirks of your workplace will determine which hearing protector is best. Only
choose hearing protection that allows employees to wear them properly and
comfortably for extended periods of time. Here are the main differences:
- May interfere with other safety
equipment (glasses, hard hat, respirator)
- Low profile headbands are designed
to prevent interference with hard hats
- Easier to remove and replace
- Best for intermittent noise exposure
- Good for dirty environments
- Uncomfortable in hot and excessively
- Best for continuous noise exposure
- Require clean hands to be inserted
- Good for tight spaces
- Good for extreme temperatures
Ear plugs are the choice of most employees. However, make sure to properly train them on how to insert ear plugs. Below you will find an image (from left to right) of a badly-inserted earplug, a semi-inserted earplug, and a properly-fit earplug.
earplugs cannot be inserted properly, then earmuffs should be used.
In the End, It Does Really Matter
most workspaces, a single layer of properly fitting ear muffs or ear plugs will
be sufficient to reach the ideal 75-85 dB of noise exposure. Double hearing
protection is recommended for employees working in noise levels above 100 dB
over an eight hour period. Ear plugs and ear muffs are the most common form of
dual protection, providing an additional 5 dB of protection.
noise levels only have to be re-evaluated when noise exposure increases beyond
what your current protection allows. Annual training should include information
on the types of protection provided, fit, and use.