Noise Reduction Rating (NRR) measures the level of sound that hearing protection devices block out. Hearing Protection Devices, also known as hearing protectors, are products that are invented and based on the ability to reduce or block out the level of sound we hear. These products are used in a wide spectrum of noise producing activities ranging from airplanes take off and music concerts to sleep-induced snoring.
Types of hearing protectors
Hearing protectors are foam or silicone earplugs and also many new devices, such as custom molded ear plugs, sound restoration devices, communication headsets, active noise reduction devices.
The regulation requires all manufacturers of hearing protection devices to provide the customers with information regarding the products effectiveness in reducing the level of noise (unwanted sound) entering our ears. Such information has to be presented on a label that is clearly visible when we buy or take decision of purchasing. Every hearing protector should have its NRR shown on the package, in decibels (dB). Usually the foam or silicone earplugs provide protection between 22-32dB.
How is measured the sound?
The device used to measure sound level is called a decibel meter. It can be used as standalone instrument and can be purchased at the technical equipment stores. You can also download it as application on your mobile phone.
Sound at 85 decibels and higher can harm your hearing. Noises above 160dB cause instant perforation of eardrum. While you are sleeping you can be disturbed by much lower levels of unwanted sound like 15-20dB.
In fact humans don’t hear all sounds. For example, marine animals can often hear sounds that humans can’t hear.
How our ears perceive the levels of sound
Most people consider 10dB change in the noise level as doubling the sound. Our ears are so sensitive that we can hear even 3dB change in the noise level. However, if the increase is 5dB it would be much more clearly noticeable. It is interesting that a normal conversation is between 44-65dB which is measured from 3-6feet distance.
Nighttime, in a quiet city area the noise levels range from 40 to 50 dB. During the day, when it is more busy and noisy, the decibels rise to 70-80 dB. Be careful with levels higher than 80 dB because if you are exposed for a continuous periods it can cause hearing loss. More than 110 dB is painful for your eardrums.
However, your ears can get accustomed to constant noises and you will accept them as less noticeable than irregular or periodic noises.
What NRR I need to block out the noise?
Many people work in a high noise levels environment and they are obliged to use earplugs in order to protect and preserve their hearing ability. Fortunately, there are good earplugs that can stop certain levels of noise. On the other hand more and more people are getting nervous and sensitive to all kind of urban noises and need earplugs to assure quite sleep at night. Most available earplugs offer dB protection between 20-32 dB. You have to keep in mind that in order to get the best of using earplugs you have to insert them carefully and properly. You can easily block out light to moderate sound levels. More efficient will be to combine with other methods and measures if possible in order to decrease the noise.