More or Less?
Double Hearing Protection
BY JEFFREY MORRILL

Many companies require Double Hearing Protection (insert HPD with an ear muff) in work areas over a certain dB level, typically 100 dB or greater. The rationale is that a single hearing protector may not provide sufficient hearing protection at these exposure levels and the addition of the second HPD will
ensure adequate protection.

A false sense of confidence evolves from this practice since the actual amount of hearing protection simply will not add up to the total NRR value of both hearing protectors. The actual combined
protection level is determined by several factors. The primary factor is how the individual is applying the insert HPD. Other factors are the condition of the ear muff (headband tension and contact
pads) and whether safety glasses or hair prevent a good seal for the muff.

Most ear muffs in existence are not new, safety glasses or long hair are common and each will greatly reduce the laboratory NRR value of the muff. It is probable that the addition of the ear muff will only add a few dB of additional noise reduction.

Therefore the insert protector becomes the primary and critical apparatus. In fact, if the insert device is poorly applied, then the ear muff becomes the primary protection device and the result is
likely to be minimal protection with “double” protectors. Unfortunately, with the ear muff over the ear it is impossible to see if the insert protector is being properly applied.

The NRR value is often used as the tool to select HPD’s. It is common for a company policy to state a minimum NRR value for the selection of protectors. Regretfully, there is often little relationship
between the NRR value and actual worker protection. NRR values are achieved in a laboratory setting
where optimum conditions will result in the best protection values possible. In the real world, employees apply the protectors in a manner that results in significant variations of personal protection.

Many studies have been conducted that demonstrate actual worker protection to be less than half of published NRR values. These studies demonstrated that 25 percent of the workers actually were achieving less than 5 dB protection.

These tests can be performed using Real Ear Attenuation Testing (REAT). This procedure is used to test for “real world” hearing protection values. The employee is given two tests with a specially
designed headset. One of the tests establishes hearing levels (similar to a hearing test) and the next test is performed after the employee inserts hearing protectors.

The difference between the tests establishes the amount of protection the employee is receiving. This is called a Personal Attenuation Rating or a PAR. The same formula is used to determine PAR that is used to determine NRR.

Clearly, it is not often that the protector is at fault when employee protection is compromised. The distinguishing factor is the method that the employee uses to insert the device. If the insert
protector achieves a good seal, good protection (often more than the NRR value) will result. If it is laying in the ear canal without a seal, virtually no protection is possible. It is not uncommon to observe protectors only partially inserted during plant tours. For those workers, “double protection” will not
achieve the intended result.

Employers can improve confidence in hearing protection (and labor relations) with a properly applied, single, insert hearing protector. If the employee achieves the published NRR value (and
that is possible), there are few noise exposure areas that would require the addition of an ear muff to reduce exposure to the 85 dBA level.

Employer assurance can be achieved through current Hearing Conservation Program (HCP) practices required by OSHA 191.95. In order of priority:
• Implement formal employee training on proper insertion of their specific HPD;
• Provide supervisor training and require formal inspection for employee use.
• Conduct up to date noise surveys and dosimetry studies;
• Limit the selection of HPD’s and offer a variety of approved protectors;
• Analysis of annual hearing testing results to identify group and individual trends; and
• Convey program results to the employees – repeat the process.

Employers can also conduct REAT testing to validate the protection being achieved by individuals. REAT testing results offer substantial documentation for both management and employees
and can build confidence in the HCP, or, expose areas of weakness to be focused on. This is not a requirement for compliance with the OSHA regulation and is a procedure that can be applied
selectively to high risk groups and work areas. It is worth considering as an adjunct to the HCP.

In summary, Double Protection may have an adverse effect on employee protection. The application of the ear muff actually prevents inspection of the proper use of the primary HPD. Single HPD’s properly worn and administered can achieve adequate protection and management expectations.

Employees should have a variety of protectors to choose from but the overall selection should be limited. Employees should be trained using the specific protector of their choice. Without supervisor
monitoring and intervention, the level of protection will be left to the employee’s discretion. Finally, employers can implement optional procedures to ensure that their employees are complying
with protection requirements. FSM  Jeff Morrill is an audiologist specializing in two-way radio communication with hearing protection systems for high noise industry and emergency response applications. He can be reached at CavCom, Inc. 866-547-4988 or www.cavcominc.com.