What is Noise Reduction Rating 

A noise reduction rating indicates the level of sound that earplugs block out when used without simultaneous noise-blocking objects. This rating applies only to earplugs and earmuffs and provides users of these devices an important analytical tool when comparison shopping.

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NRR Ratings

The highest NRR rating for earplugs is 33, and the highest available NRR rating for earmuffs is 31. These values reflect the level of noise protection available for each device when worn alone. Combining earplugs with earmuffs can offer a NRR protection level of 36. Manufacturers produce different types of earplugs and earmuffs to reach these ratings. Generally, higher-quality devices that cost more receive a higher NRR rating.

Types

Disposable earplugs typically receive NRR rating in the low to mid 20s.
Disposable earplugs include wax plugs, foam plugs and most unspecialized, general plugs. Reusable earplugs include specialized plugs such as those manufactured for flying and those specially made for shooting and hunting. The highest NRR-rated earplugs and earmuffs support reuse.

How do I use the Noise Reduction Rating (NRR) value to determine the protection provided by a hearing protector?

NIOSH recommends using subject fit data based on ANSI S12.6- [or the most current edition] to estimate hearing protector noise attenuation.

If subject fit data are not available, NIOSH recommends derating hearing protectors by a factor that corresponds to the available real-world data. Specifically, NIOSH recommends that the labelled NRRs be derated as follows:

• Earmuffs &#; Subtract 25% from the manufacturer&#;s labelled NRR

• Formable earplugs &#; Subtract 50% from the manufacturer&#;s labelled NRR

• All other earplugs &#; Subtract 70% from the manufacturers labelled NRR

1. When the noise exposure level in dBC is known, the effective A-weighted noise level (ENL) is:

ENL [dB(A)] = Workplace noise level in dBC &#; derated NRR

2. When the noise exposure level in dB(A ) is known, the effective A-weighted noise level is:

ENL = Workplace noise level in dB(A) &#; (derated NRR -7)

There are other single-number ratings available. For details refer to the Canadian Standard CSA Z94.2. Another single number rating is based on (Subject Fit) Real Ear Attenuation measurements, known as Single Number Rating (Subject Fit 84th percentile) and abbreviated as SNR (SF 84) (for details see ANSI Standard S12.6). &#;SF 84&#; indicates that 84% of the users in a well-run hearing conservation program are expected to receive at least that much protection.

MORE ABOUT dB BLOCKERS®

We live in a noisy world. Some noises can damage our hearing, leading to hearing loss, tinnitus (ringing in the ears), and difficulty communicating especially in background noise. Permanent noise-induced hearing damage is incurable. If you cannot reduce your noise exposure by turning down the volume, moving away from the sound, or limiting the time you are exposed, hearing protection is your only option. But hearing protection comes in so many styles, materials, color, and sizes &#; how can you know which is best for you? National Protect Your Hearing Month is the perfect opportunity to discuss tips for picking the right hearing protector.

Figure 1: Selection of different hearing protection devices &#; Earplugs, Earmuffs, and Earbands

1) Know How Much Noise Reduction You Need

Obviously, the first consideration in choosing a hearing protector is whether it will block enough noise to reduce your exposure to a safe level. The good news is that most industrial noise exposures are less than 95 dBA, which means most workers require no more than about 10 dB of noise reduction to meet the NIOSH Recommended Exposure Limit of 85 dBA. Almost any hearing protector, when fit correctly, can provide 10 dB of sound reduction. If you do not know the noise levels at your worksite, you can measure them with an app such as the NIOSH Sound Level Meter.

Louder environments demand higher levels of noise reduction, but beware of reducing sound too much. Just as too little light can make it just as difficult to see as too much light, too little sound can make you feel isolated and less aware of their surroundings. Overprotection can be counterproductive, as you may feel the need to remove your hearing protector to hear someone speak or listen to your equipment. Aim for just enough noise reduction to bring your exposure down to 75-85 dBA.

The Noise Reduction Rating on hearing protector packaging represents the amount of noise the hearing protector blocked when tested in a laboratory, but workers usually get much less noise reduction on the job. The best way to know how much noise reduction you are getting from a hearing protector is by fit-testing. If fit-testing is not available at your workplace, you can check earplug fit by counting out loud while slowly cupping and uncupping your hands over your ears; if you have a good fit, your voice should sound about the same as you cup and uncup your ears. NIOSH QuickFitWeb can also be used to check if you are getting more or less than 15 dB of sound reduction.

If you are exposed to noise levels 100 dBA or greater (such as chainsaws or jackhammers) or if you are exposed to impulsive sounds (such as nail gun or weapons noise), you should wear double hearing protection (earmuffs over earplugs).

2) Think About Your Worksite and Job Tasks

Workplace characteristics beyond noise levels also need to be considered in choosing the right hearing protector. For example, do you have to wear other head-level personal protective equipment (PPE), such as eye protection, a hard hat, or a respirator? Eye protection (and even some eyeglasses) can interfere with the seal of an earmuff around the ear, allowing sound to leak into the ear. Earmuffs can interfere with the fit of hardhats or helmets; some muffs have a &#;low-profile&#; headband or are designed to be mounted directly onto a hardhat or helmet, eliminating this problem. Make sure that your hearing protection is compatible with other safety equipment you use at work.

Consider also whether the noise at your job is continuous or if it stops and starts at various times during the day. Do you stay in the same place for most of the workday, or move from one area to another? Earmuffs are easier to remove and replace than earplugs, so they may be better for intermittent noise exposures. If earmuffs are not an option due to other issues (e.g., compatibility with other PPE), pre-formed earplugs may be easier to remove and replace than foam plugs. Level-dependent or sound restoration hearing protectors can also be useful for intermittent exposures; these types of hearing protection allow sound to pass through when the background noise levels are low and become protective when noise levels increase.

Do your hands frequently get dirty at work? If so, avoid using foam earplugs which must be rolled down with your fingers before insertion, unless hand-washing facilities are readily available and you have time to wash up each time you need to insert the earplugs. Do you work in a tight space? Earmuffs may not be compatible when working in a confined area. Is it very hot or very cold where you work?   Earmuffs can be uncomfortable in hot environments; earmuff cushions can become ineffective in very cold environments.

Finally, think about how frequently you need to hear speech while wearing hearing protection. If spoken communication is common, or if high fidelity sound is important for other reasons (e.g., musicians), flat attenuation hearing protectors may be helpful. Special communication headsets can also improve speech communication in very loud environments.

Contact us to discuss your requirements of Zh Tech Hearing Protector. Our experienced sales team can help you identify the options that best suit your needs.

3) Decide What is Most Comfortable and Convenient

Once you have narrowed your selection down to hearing protectors that are appropriate for your noise exposure and compatible with your worksite and job tasks, the choice is completely up to you! However, hearing protection only works if you wear it consistently and correctly every time you are exposed to hazardous noise, so choose a protector that is comfortable and convenient.

Many people find earplugs more comfortable than earmuffs, especially when worn for long periods of time or in in hot environments. Earplugs are lightweight, easy to store, and convenient to keep on hand for unexpected exposures. However, earplugs may be harder to learn to fit properly. Some earplugs come in different sizes, so you may need help determining which size is correct for you. If your ear canals are very narrow or very curvy, it may be difficult to find an earplug that will fit. Earplugs are usually inexpensive, but they need to be replaced frequently; some earplugs are designed to be used once only and then discarded.

Earmuffs, on the other hand, are generally one-size devices. Many people find them easier to fit properly and consistently. Earmuffs are easier to remove and replace quickly, so they can be preferable for intermittent use. They are bulkier than earplugs and may be uncomfortable in warm places or tight spaces. They are more expensive, but more durable and last longer than earplugs.

Hearing health relies on knowing how to protect your hearing and how to select the right form of hearing protection. This National Protect Your Hearing Month, take a few minutes to make sure you are using the best hearing protection for your work tasks. Then, wear it every time you are exposed to noise levels above 85 dBA. Your ears will thank you!

CAPT William J. Murphy, Ph.D., is a research physicist with the NIOSH Division of Applied Research and Technology.

Christa L. Themann, MA, CCC-A, is a research audiologist with the NIOSH Division of Applied Research and Technology.

CAPT Chucri (Chuck) A. Kardous, MS, PE, is a research engineer with the NIOSH Division of Applied Research and Technology.

CAPT David C. Byrne, Ph.D., CCC-A, is a research audiologist with the NIOSH Division of Applied Research and Technology.

Additional resources:

NIOSH Personal Protective Equipment (PPE)

Best practice bulletin: Hearing protection-emerging trends: Individual Fit Testing

Hearing protection &#; OSH WIKI

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