Help your employees make the most of the hearing protection devices (HPDs) they wear by verifying that the noise reduction provided is adequate and that the HPDs are properly used, maintained and replaced.
The attenuation value (SNR, HML and Octave Band) shown on the packaging of hearing protectors is a description of how much noise reduction was measured on a group of well-trained hearing protection users who wore the HPD correctly in a laboratory test in accordance with appropriate harmonised European standard.
As the science has evolved in hearing protection, it is becoming generally recognised that the best way to ensure the adequacy of a hearing protector for any specific worker is to the conduct fit testing to confirm that the expected level of attenuation is achieved (i.e., the proper type of protector was selected and is being used correctly). 3M strongly recommends the fit testing of hearing protectors. In Europe, the benefits of hearing fit testing are described in the European guidance document EN 458:2016 as a way of improving field performance of hearing protectors. The guidance document also explains how to estimate sound level under the hearing protector using SNR, HML and the Octave Band method.
The measurements required to use the three methods of estimating sound level are:
To use the SNR method for estimating effective sound level at the ear, you simply subtract the SNR value from the overall C-weighted sound pressure level.
For example, if the measured C-weighted sound pressure level is 100 dB and the SNR value of a chosen hearing protector is 25 dB, the calculated A-weighted sound pressure level to the ear when wearing the hearing protector is 75 dB.
Measured sound level dB(c) - SNR rating of '3M™ E-A-R™ Classic' = Protected Exposure (inside the ear, behind the hearing protector)
=95dB - 28dB = 67dB (A)
The practice of applying a nominal correction factor (derating) , to the laboratory generated data is done to account for the difference between the stated attenuation on the product packaging and the attenuation workers get when on the job. Within the European Union, each member country has adopted different approach regarding derating which may not only differ by country but also by product types. For example, in the United Kingdom there is a flat 4dB reduction in the overall attenuation for all types of hearing protection devices, whilst in Germany, the reduction varies between 3 dB (for custom moulded earplugs) and 9 dB (for more conventional earplugs).
While derating is intended to help assess realistic attenuation achieved by the wearer, there is an equally credible approach in the form of fit testing which is designed to measure the actual attenuation achieved by the wearer.
Where operator noise exposure exceeds 105 dB(A), especially if there is a substantial amount of low frequency content e.g. compressor, generator room etc., dual protection may be required.
As a rule of thumb, wearing earmuffs together with earplugs provides approximately 6 dB more noise reduction than either device worn by itself. The extra protection provided varies depending on the frequency of the sound. To estimate the combined attenuation, simply add 6 dB to the higher of either earmuffs or earplugs attenuation value.
For example, the SNR value of 3M Peltor X4A is 33 dB and 3M EAR Classic is 28 dB. When worn together, the combined protection of these two hearing protection devices will be 39 dB.
Always follow the User Instructions provided with the hearing protectors for fitting, cleaning & storage, and replacement of HPDs. In general, replace hearing protectors when they are damaged or no longer provide an effective noise-blocking seal.
Care: Headband and outside of cups are washable. Foam inserts inside cups are not. Replace bands when: damaged or they no longer provide enough tension to hold cups tightly over ears. Replace cushions and foam inserts: every six months or sooner if they are damaged or are no longer soft and pliable.
Care: Bands and reusable tips are washable. Foam tips are not. Replace bands when damaged or they no longer provide enough tension to hold tips tightly in or on ears. Replace tips when they are damaged or are no longer soft and pliable.
IMPORTANT NOTE: This information is based on selected current national requirements. Other country or local requirements may be different. Always consult User Instructions and follow national regulations. This website contains an overview of general information and should not be relied upon to make specific decisions. Reading this information does not certify proficiency in safety and health. Information is current as of the date of publication, and requirements can change in the future. This information should not be relied upon in isolation, as the content is often accompanied by additional and/or clarifying information. All applicable national laws and regulations must be followed.
Contact your local 3M office for further information.