Noise Reduction Ratings Explained
Noise Reduction Rating (NRR) is a unit of measurement used to determine the effectiveness of hearing protection devices to decrease sound exposure within a given working environment. Classified by their potential to reduce noise in decibels (dB), a term used to categorize the power or density of sound, hearing protectors must be tested and approved by the American National Standards
(ANSI) in accordance with the Occupational Safety & Health Administration
(OSHA). The higher the NRR number associated with a hearing protector, the greater the potential for noise reduction.
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How does NRR change decibels of exposure?
When hearing protection is worn, your level of exposure to noise is based on the NRR rating of the protection device being used. Keep in mind, however, that while the NRR is measured in decibels, the hearing protector being used does not reduce the surrounding decibel level by the exact number of decibels associated with that protector’s NRR. For example, if you are at a rock concert where the level of noise exposure is 100 dB and you are wearing earplugs with an NRR 33dB, your level of exposure would not be reduced to 67 dB. Instead, to determine the actual amount of decibel deduction applied (when decibels are measured dBA which is the most common), you take the NRR number (in dB), subtract seven, and then divide by two. Given the previous example, your noise reduction equation would look like the following: (33-7)/2 = 13. This means that if you are at a rock concert with a level of noise exposure at 100 dB and you are wearing a hearing protector with an NRR 33 dB, your new level of noise exposure is 87 dB. If you are wearing a product with an NRR of 27 it would deduct 10 decibels (27-7/2=10).
*To maximize noise reduction, hearing protectors must be worn properly.
How does wearing dual hearing protectors change NRR?
When hearing protectors are worn in combination (i.e. earplugs AND earmuffs), rather than adding the two NRR numbers together, you simply add five more decibels of protection to the device with the higher NRR. For example, using 3M™ E-A-R™ Classic Earplugs
(NRR 29) with 3M™ Peltor™ H7 Deluxe Earmuffs
(NRR 27) would provide a Noise Reduction Rating of approximately 34 decibels.
What is considered excessive noise?
While the amount of on-the-job noise exposure can be determined through various testing devices, excessive noise is generally defined as exposure to 85 or more decibels of sound over an 8 hour period.According to OSHA,hearing protection is required for all employees at this degree of exposure. This OSHA Action Level, however, will vary depending upon the decibel level of the surrounding environment. For example, if a worker is exposed to 100dB in a 2 hour period, he or she is also required to wear hearing protection. Each hearing protector product is required to meet the ANSI S3.19-1974 testing of NRR levels.
In all cases where the sound levels exceed the values shown below, a continuing, effective hearing conservation program should be administered.
For a better grasp of industry standards, here are a few of the most common producers of noise levels that OSHA considersto be dangerous: lawnmowers, rock concerts, firearms, firecrackers, headset listening systems, motorcycles, tractors, power tools and industrial machinery. The use of hearing protection is strongly recommended during continued exposure to any of the previously listed environments, as all can deliver sounds in excess of 90 decibels.
150 dB = Rock Concerts at Peak
140 dB = Firearms, Air-Raid Siren, Jet Engine
130 dB = Jackhammer
120 dB = Jet Plane Take-off, Amplified Music at 4-6 ft., Car Stereo, Band Practice
110 dB = Machinery, Model Airplanes
100 dB = Snowmobile, Chain saw, Pneumatic Drill
90 dB = Lawnmower, Shop Tools, Truck Traffic, Subway
80 dB = Alarm Clock, Busy Street
70 dB = Vacuum Cleaner
60 dB = Conversation, Dishwasher
50 dB = Moderate Rainfall
40 dB = Quiet room
30 dB = Whisper, Quiet Library
Save Your Hearing
Exposing yourself to high decibel environments can result in permanent damage to your hearing. In the event you find yourself in one of these environments, protect yourself with the proper hearing protection. If you have questions about any of the hearing protection products on our website, please feel free to call our customer service department. Our staff is dedicated to keeping your hearing safe and sound.