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What Are Noise Reduction Ratings?

Hearing protection by the numbers

What are noise reduction ratings?

Your ability to hear is a delicate thing. It can easily be damaged by loud noise. The hearing process begins with sound waves or vibrations that enter your ear. The ear canal sends those sound waves to your brain, where they are interpreted into words or music or a jet plane taking off. Your ear is made up of tiny, precise parts, finely made to do certain things. When they are damaged, they may not recover, resulting in hearing loss. The purpose of ear protection devices is to reduce the intensity of the sound.

Sound and its variety of loud and soft levels are measured in degrees of loudness called decibels, or dB. The higher the number of decibels, the louder the sound. In many industries, employees use hearing protection devices to cover their ears. Every device has a rating that determines how much sound it will cancel out.

Rating the Amount of Protection

The Noise Reduction Rating, or NRR, on an ear protection device lets the wearer know how much protection it will supply. There are various kinds of hearing protectors available, including headsets, earplugs, and earmuffs.

Are the ratings trustworthy? Not necessarily, according to federal agencies like the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). They recommend derating the NRR listed on the device you use. The advice on how much to derate is not always the same. For instance, OSHA recommends derating every protection device by 50%, while NIOSH recommends derating earplugs by 50% and earmuffs by 25%. When deciding which device to use, choose the one with the most protection.

There is also the single number method of rating ear protection devices, called the SNR. It is mainly used in Europe and is reported to be a simpler method to navigate.

noise reduction rating chart

Unless your work environment is in noisy surroundings, and you regularly wear ear protection already, you may not be aware of the noise levels of different sounds.

Here are some decibel levels, from quietest to loudest, with examples of typical noises at those levels:

Decibel Scale - measure the different levels of sound - SoundEar Int.

In prolonged noise exposure, at dB levels over 85, to avoid hearing damage, you should wear protection. Some noises, 130 decibel levels and above, can actually be painful if you’re exposed to the sound for 30 seconds or more. Ear protection is vital.

what is a good noise reduction rating?

It’s important to know what your noise exposure level is before you can select the proper ear protection, or the proper NRR. As a rule, most industrial processes produce noise levels that are at 95 dB or less. To meet the NIOSH recommended exposure limit of 85 dBA, you would only need 10 NRR to be in the safe zone.

While sound is measured in decibels (dB), there is an added nuance of measurement called the dBA. The scale for dB is based on intensity, while the dBA scale notes how the human ear responds to the sound as well as the dB. It’s a more accurate measurement, since not all ears hear sounds and tones in exactly the same way. The “A” comes from “A-weighted decibels,” a designation that describes the method of measuring.

Knowing the right NRR rating for your ear protection is the first step toward selecting the correct ear protection device. All devices have different ratings and functionality. Obviously, you want to protect your hearing with the best type of equipment you can get. People use ear protection in many situations; industry is just one. Those who shoot firearms, especially at an indoor target range where sound can be amplified, need ear protection as well. The dB of a gunshot is at the top of the list.

Generally, the higher the NRR number, the more protection you have from the sound level. NRR numbers go from the low teens to about 30. Let’s take a gunshot as an example. The dB of a gunshot is 140. If you have ear protection with 30 dB, that brings it down to 110, still over the safe limit. However, everyone’s ears are different. Devices also fit differently on different people, so it’s important to fit them properly.

how do you calculate nrr?

The rating is tested by following the American National Standards Institute (ANSI) standard from 1974. The test requires 10 people. Each person is fitted with the device in question using a process known as Real-Ear Attenuation at Threshold, or REAT. The sound exposure is set to nine different frequencies (125, 250, 500, 1000, 2000, 3150, 4000, 6300, and 8000 hertz), and the test measures the reduction in sound for each. The researcher gains a total of 30 results for each person. The numbers are averaged, and the result is the NRR number.

best headphones for noise reduction

People are using noise-canceling headphones more than ever these days. Kids use them to attend school from home, and travelers use them to nap on airplanes. As more of us work from home, we find we live next door to people who don’t work from home. They are mowing their lawn when we are trying to write that final report, and we need quiet! All headphones come with different NRR ratings, and you should find the rating that is required for your workplace or wherever you plan on wearing them. The highest rating available is 33 NRR, suitable for wearing at an indoor shooting range.

The best noise reduction headphones should be lightweight and comfortable, no matter how long you wear them. Look for headbands that are padded and adjustable. The material that lies flat against your ear should be soft and breathable. This should also be easy to clean and replace when necessary. If the earpads require replacing, you want to avoid having to purchase a whole new headset. The MT-370 from Plant-Tours meets all those features and more.

Designed for extra noisy environments like you might encounter on a factory tour, the PT-250 Max Noise Headphones are the highest grade headset Plant Tours offers. The 12-ounce headphones’ 24 NRR removes as much sound as possible and allows you to hear what’s going on around you. An over-the-head and rear head guard lets you fit a hard hat comfortably over the set.

These protective devices work well in real-world, high-noise environments such as manufacturing, engineering, mining, woodworking, and automotive shops. You can subtract the designated amount of noise easily with these headphones.

If you want a lighter option (weighing only 2.8 ounces) check out the MT-350 from Plant-Tours. This headset will deliver the ear protection you expect, and it wraps around the back of the head rather than over the top. These headphones are recommended for low to moderate noise levels. They have a Push to Talk option and fit the user comfortably even while wearing a hard hat. Communication in high noise environments has never been easier!

organizations working toward preventing hearing loss

NIOSH provides information and programs that work toward preventing hearing loss due to the level of noise in the workplace.

ANSI is the organization that sets standards for nearly all industry or healthcare fields when it comes to noise levels. You’ll see the acronym ANSI on hearing protection devices with some numbers, referring to the code of compliance. This dates back to 1974 when the Acoustical Society of American (ASA) released their first ANSI Method for the Measurement of Real-Ear Protection for Hearing Protectors and Physical Attenuation of Earmuffs.

OSHA is heavily involved in workplace safety. According to their requirements, employers must have a hearing conservation program whenever the noise level is over 85 dB for eight hours.

The Environmental Protection Agency (EPA) has fought against noise pollution via the Clean Air Act Title IV, which acknowledges that unwanted noise has an adverse effect on citizens’ lives. The link between the permissible noise exposure level and health has been established. Noise can be the cause of health problems such as high blood pressure, sleep disruption, and hearing loss.

It’s necessary for workers in noisy environments to wear hearing protection that shields them adequately from excessive, unhealthy levels of noise. Knowing how to take care of your hearing is important, and exercising proper hearing care now can result in added benefits later in life.