Fit for Purpose: Is your Tactical Hearing Protector up to the Job?

Neal Muggleton, Strategic Marketing Director, Honeywell Safety Products, talks about how to prevent Noise Induced Hearing Loss.

The world of hearing protection is becoming increasingly sophisticated. Long gone are the days of pushing cotton wool into ears and hoping for the best. Today’s market is littered with earmuffs and earplugs of all shapes, sizes and materials. Some offer functions to allow sounds through the hearing protector – either by passive filters or electronic circuitry. Others can connect to communication radio, mobile telephones or personal entertainment devices.

High end hearing protectors sometimes employ electro-acoustic technologies to provide Active Noise Reduction, beneficial for low frequency noise. There are even products offering features unrelated to hearing protection that are beneficial at influencing the ‘gadget’ audience to buy.

However, the underlying primary purpose of the modern hearing protector is the same as its cotton wool predecessor; to prevent Noise Induced Hearing Loss (NIHL).

Correct fitting is Paramount

Considering the hearing protector in a military combat setting; it is vital that it significantly contributes to the prevention of NIHL. It must however, prevent users from becoming disconnected and isolated from their surroundings when wearing the protective equipment. It must also ensure that the two-way radio communication through the connected radio is highly intelligible and reliable across all noise scenarios and dB levels.

Paramount in the prevention of NIHL is the correct fitting of the protective device; this applicable to over-the-ear ‘muffs’ or in-the-ear ‘plugs’. Not having the device fitted well will reduce its effectiveness and will increase the incidence of over-exposure to noise, which will contribute to NIHL. In some cases with earplugs, the level of noise within the ear canal can increase due to resonance within the ear cavity caused by the poorly fitted earplug.

Having a correctly fitted plug will substantially improve communication intelligibility. In the case of the systems employing an in-ear microphone, two-way communication through the radio will be improved.

Headset NRR does not equal real-world attenuation

Safety regulatory legislation requires that workers are provided with information and training when they are exposed to certain noise conditions. Studies have shown that specific product training, covering the fitting of the hearing protector is necessary to ensure that the best performance benefit is realised.
In one study conducted by Kevin Michael PhD and Cindy Bloyer “Hearing Measurement on End User”, 192 industrial workers using a flanged multi-use earplug were assessed. The earplug was rated to give a laboratory Noise Reduction Rating (NRR) attenuation of 27dB . Using the Howard Leight ‘VeriPro’ fit testing product, it was possible to measure and quantify the actual level of attenuation that each user achieved. Figure 1.0 shows the results.

The study revealed a wide variation of real-world attenuations for the 192 workers ranging between 0 to 38dB. This variation commonly occurs in actual use and may be caused by the wearer not inserting the earplug correctly to make it feel less ‘intrusive’.
Researchers in this study took the workers with the lowest attenuation, and retrained them in using the hearing protector properly. This resulted in an average 14 dB improvement in measured attenuation.

The conclusion drawn from the study indicated that the published NRR for a hearing protector does not necessarily equal the attenuation of the device in real-world practical applications.
It further indicated the benefit of undertaking specific earplug fitting training.

Fit Testing

Earplug fit-testing identifies a person’s individual earplug attenuation. Fit-testing provides Hearing Conservation Program managers with a way to provide a more personal approach to training and evaluation and provides hearing protection users with individual feedback about the fit of their earplugs.

Since the 1970s, hearing protectors have been sold with a rating number on the package showing the amount of estimated protection that a hearing protector CAN provide – the Noise Reduction Rating [NRR]. But the NRR is simply an estimate of protection based upon population averages, not measurement of actual rotection for any one individual. It is a population estimate based upon ten subjects tested in an acoustical lab.
Although the development of individual fit-testing for hearing protection is a new trend, the concept of fit-testing of other personal protective equipment is not, such as that for respirators.
The goal is to provide an individual user with feedback on whether he/she is properly wearing a given hearing protector and that it offers sufficient protection for the environment or condition in which it is to be used. Once the appropriate attenuation is determined, fit- testing enables the user to focus on how to insert and wear earplugs to attain proper protection.

Headset auto fit test.

The findings of the Michael / Bloyer study are particularly important when considering the need of the military user of in-ear tactical hearing protection and communication systems.

It is universally accepted that a correctly and well fitted earplug is the key aspect of achieving high levels of hearing protection and two-way radio communication clarity.

The QUIETPRO Intelligent Hearing System automatically tests the ‘fit’ of each earpiece and earplug. If for any reason the fit is insufficient, the QUIETPRO system will provide an advisory alarm and spoken guidance as to which earplug is poorly fitted. In the worse case that both sides are poorly fitted, this is also reported to the user.

This fit-test happens automatically when the device is turned on and takes only a few seconds to complete. At the end of the ‘fit-test’ the QUIETPRO immediately enters operational mode. If the earplug fitting was performed sufficiently well giving an adequate level of attenuation, no advisory alarm or guidance is presented. If an alarm is received, it is still possible to operate with the QUIETPRO, but the user will know that the level of protection being received could be improved.

This is a fundamental advantage of QUIETPRO compared to other headset systems. When using QUIETPRO, users have a high degree of confidence that they are being protected. Without the QUIETPRO, it simply is not possible to know the level of protection until the user receives the results from a hearing examination.
With the vast array of hearing protectors and the myriad of options and features being offered, deciding which are the most important for your users or hearing conservation programme can be bewildering.

Focusing on the first principles of hearing protection, reducing the level of noise entering the ear in an appropriate way is vital. The primary way to achieve that protection is to select the right device that provides the correct level of attenuation, but to ensure that it is fitted correctly.

Without fit-training and fit-testing, users will not know if they are being protected until it is too late. With so much at stake, isn’t it important to know that the hearing protector being used is fit for this critical purpose?