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What is hearing protection fit testing?

Many people don’t know that it is possible to conduct fit testing for hearing protection devices (HPDs). Conducting this type of fit testing has numerous benefits; one of the biggest is that it helps ensure workers are properly wearing hearing protection devices to help prevent noise-induced hearing loss.

Our four-part series sheds light on the importance of hearing protection fit testing and gives insight into the 3M™ E-A-Rfit Dual-Ear Validation System, the only quantitative fit-test system that objectively lets you measure the effectiveness of different types of 3M™ Earplugs and Earmuffs.


How is ear fit testing possible?

It can be difficult to determine what level of protection your employees are receiving from their hearing protectors. But this is now possible when you use a field attenuation estimation system (FAES) to conduct ear fit testing. FAES is a quantitative method for individually fit testing hearing protection devices (HPDs). This article describes the 3M™ E-A-Rfit Dual-Ear Validation System and the value it can provide for hearing loss prevention programs (HLPP) across different types of workplaces and industries.


What is the technology behind 3M’s hearing protection fit testing?

The 3M™ E-A-Rfit Dual-Ear Validation System is based on field microphone-in-real-ear (F-MIRE) technology. The system consists of a specially designed loudspeaker equipped with a digital signal processor that allows for a consistent presentation of the test signal and real-time communication between the microphones, speaker and software.

Specially designed, dual‐element microphones make it possible to measure the sound level at two different locations and for both ears simultaneously. The external microphones measure the level of the test signal outside the ear. The internal microphones are connected to one of the specially modified probed hearing protectors to allow measurement of the sound level inside the wearer’s ear canal while the hearing protector is worn.

The 3M™ E‐A‐Rfit™ Dual‐Ear Validation System also has earmuff testing capabilities. Both ears are accurately measured simultaneously, and in less than 5 seconds, a personal attenuation rating (PAR) is displayed.


Ear fit testing starts with PAR

The measurement of attenuation for a fit-tested hearing protector is displayed as a PAR. To be sure that your employees are getting the hearing protection they need, you should have a record of the PAR of every employee. Hearing protector ratings, including single numbers ratings such as the noise reduction rating (NRR) or SNR (SF84) or CSA Class, are derived from measurements gathered in a carefully controlled laboratory environment.

Although the ratings are an accurate measurement of the capabilities of a particular hearing protector under the specific test conditions, they may not represent what an individual worker will achieve when the device is worn in the workplace. Most employees receive adequate protection, while some may not if they are not using the hearing protector correctly or have not chosen the correct size or style.

Note the wide range of PAR values tested on four earplugs considered high attenuating according to their labeled values:

(Chart source:


Why use PAR vs. the labeled protection value?

The chart below displays PAR values for earplug #4, measured on 157 employees. The blue represents the workers with PAR values (minus their uncertainties), who achieved at least the US OSHA derating value or more. But the PAR values in red indicate the workers would have not met the derated criteria. This highlights the importance of using individual worker attenuation data rather than labeled values, even when derated, to predict user protection.

(Chart source:

Stay tuned for part two in our series on hearing protection device fit testing and how the 3M™ E-A-Rfit Dual-Ear Validation System works to make the process easy.

Visit us online to learn more about the 3M™ E-A-Rfit Dual-Ear Validation System and to request a demo.