Right Fit Test, Right Now 3M™ E-A-Rfit™ Dual-Ear Validation

The Technology    

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 2 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 3M™ 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.

It 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 protection they need, you should to know the PAR of every employee. Hearing protector ratings such as the noise reduction rating (NRR), the single number rating (SNR) and the sound level conversion (SLC80) 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. 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 (Figure 1). Note the wide range of PAR values tested on 4 earplugs considered high attenuating according to their labeled values.

Why use PAR vs. the labeled value?

Figure 2 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 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.

WHO do you test and who conducts the testing?

Who Should Be Tested?

The target population is presumably the group of employees expected to be at risk for noise-induced hearing loss (NIHL) and may either be limited or broadly defined. Examples of target populations include:                                                                                                                                                             

•  Newly hired employees
•  Employees with a measured temporary threshold shift (TTS) or standard threshold shift (STS)
•  Subset of employees who work in the highest noise areas or are required to wear dual hearing protection                                     
•  Subset of employees who are at the margins of inclusion for mandatory hearing protection                                                                      
•  Subset of employees exposed to ototoxic chemicals as well as to noise
•  All employees who qualify for inclusion in the hearing conservation program
•  All employees regardless of noise exposure at work

Who Conducts the Fit Tests and/or Manages the Fit-Test Program?

In general, those responsible for the HLPP will manage the fit-test program. Examples of personnel typically responsible, previously referred to as operators, for conducting fit tests include:

•  Industrial hygienists
•  CAOHC certified personnel
•  Safety professionals
•  Occupational health nurses
•  Vendor-trained personnel
•  Independent or authorized service providers

WHY use the 3M™ E-A-Rfit™ Dual-Ear Validation System?

Incorporating fit testing within an HLPP results in a multitude of benefits. The list below highlights the most compelling reasons why you should use the 3M E-A-Rfit Dual-Ear Validation System.

1. Identify workers with low PARs who are consequently at risk for developing NIHL.
2. Verify the performance of HPDs without relying on laboratoryderived labels and derating schemes that are intended for groups of employees and not individual workers.
3. Train and motivate employees on the proper use and fit of HPDs.
4. Select and assign HPDs based on noise exposures, expected protection levels and the anatomy of the worker’s ear canal.
5. Train personnel responsible for teaching employees the proper use and fit of HPDs.
6. Provide a useful standard-threshold-shift (STS) follow-up procedure that can be used to determine whether the problem may be related to either the fit or the attenuation capabilities of the HPD.
7. Provide data that may be accepted by regulatory agencies as a better alternative to using labeled attenuation values and derated to assess HPD adequacy.
8. Audit departments to evaluate overall HPD effectiveness and suitability.
9. Provide potentially useful documentation to demonstrate hearing loss prevention efforts conducted by a company that go beyond regulatory requirements.