To 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?
The first step is to know the noise levels your employees encounter each day. Workplace noise measurements 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 program.
When 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.
Double 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?
For 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.
To determine how NRR rating affect dB, take the NRR number subtract 7 and divide that number by 2.
In our example: (30 – 7) / 2 = 11.5
A 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.
If 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.
In 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
Now, let’s calculate the dB reduction of our dual protected worker with 35 NRR.
dB reduction = (35 – 7) / 2 = 14
A 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
For 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 questions:
- 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?
Just 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.
Ideally, 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 exposure.
Should You Use Ear Plugs or Ear Muffs?
The 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 cold climates
- Best for continuous noise exposure
- Require clean hands to be inserted properly
- 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.
If earplugs cannot be inserted properly, then earmuffs should be used.
In the End, It Does Really Matter
For 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.
Workplace 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.