All You Need to Know About Noise Reduction Rating (NRR)
The danger of exposure to high noise levels is real. In any noisy work environment, adopting appropriate hearing protection measures is essential to prevent permanent hearing loss.
What should I know about hearing protection devices?
Workers in an environment where the sound or noise level exceeds 85 decibels (dBA) should wear hearing protection. This helps minimize the risk of hearing loss and reduce the noise exposure level.
Whenever hearing protection is required, you should put in place a complete hearing conservation program that covers:
- Noise assessment in the workplace.
- Employee training on the use of hearing protectors.
- Regular audiometric testing.
- Record keeping.
- Selection, maintenance, and inspection of hearing protection equipment.
* The efficiency of hearing protection devices decreases when removed (even for a short period), if it is worn only from time to time, and if it doesn’t fit properly.
What are the types of hearing protectors available?
- Earplugs: inserted in the ear canal and can be pre-molded or moldable. 3M offers a wide variety of disposable, reusable, and custom-made earplugs.
- Semi-insert earplugs: two earplugs retained over the ends of the ear canal by a rigid headband.
- Earmuffs: ear cushions made of sound-attenuating materials that fit over the ear, held together by a headband. 3M Earmuffs are offered in various positions: over the head, behind the head, and cap attached.
What is Noise Reduction Rating? (NRR)
Noise Reduction Rating (NRR) is a system used to determine the effectiveness of hearing protectors to reduce sound exposure. This unit of measurement is powerful since it easily indicates the functionality of a device and its ability to protect the worker.
Expressed in decibels (dB), the values range from 0 to approximately 35. The higher the NRR, the greater the noise attenuation.
For example, a noise-reduction headset with an NRR of 30 dB is designed to reduce noise exposure by 30 dB in a laboratory setting.
Is the NRR accurate?
The short answer is… no. NRR is a bit optimistic, and the actual protection of a device is usually lower than what is stated.
The NRR is a laboratory test and is conducted in highly controlled facilities. The real-world results are different because of poor fit, lack of proper training on the hearing protection device, and enforcement.
How can I get a good protection number?
To get a more realistic estimate of the protection provided by a hearing protector, it is recommended that the noise reduction rating.
To approximate an NRR, a little math is needed. This is a simplified version, and you can get all the information on the NRR derating plan in the CSA Z94.2-14 Hearing Protection Devices Standard.
Simplified formula:
- Subtract 7 from the listed NRR value.
- Divide the result by 2.
- Subtract the result from the noise exposure level (in decibels) of your environment.
Let’s put it in action:
Let’s say you’re exposed to a noise level of 100 dBA. You have earmuffs with an NRR of 30.
- Subtract 7 from 30 = 23.
- Divide this result by 2 = 11.5.
- Subtract the result (11.5) from the noise exposure level of your environment (100) = 88.5 dBA.
This means that you would be exposed to 88.5 dBA and not 70 dBA, as the NRR might suggest.
The NRR is an essential tool for selecting the right hearing protection
To get optimal protection, hearing protection devices are indispensable in any noisy work environment. With the help of NRR labels, you can better understand noise exposure levels and get an approximate idea of how much a specific hearing protection device truly protects your workers.
