Brad Witt

Safety professionals in the energy sector may be concerned about the use of hearing protectors in potential arc flash environments.

Ideally, the best way to know if a worker is protected from hazardous noise is to take a noise dosimetry measurement under the hearing protectors — that is, place a microphone at the eardrum. This concept of in-ear dosimetry is now available in a product called QuietDose™.

There definitely are several methods of measuring real-world attenuation on workers wearing ear plugs.

Instead of relying upon the population estimates of the NRR, a safety manager can now measure each worker’s protection level.

While each method of fit-testing has its own merits, one of the most popular methods is called VeriPRO®.

And as the name implies, it verifies the protection achieved by a worker wearing ear plugs.

Since the EPA promulgated its Noise Reduction Rating (NRR) on all hearing protector packaging since 1974, many studies have shown that attenuation achieved in the real-world is sometimes far below the laboratory NRR. There are a number of good reasons for this difference: users in the real-world might not receive proper training, or might adjust their hearing protectors for comfort rather than protection, or they may intentionally compromise the fit in order to hear co-workers and machine noises more clearly. 

It seems plausible that if a well-fit ear plug blocks 30 dB of noise, then a half-fit ear plug must block 15 dB of noise. Unfortunately, the math of hearing protection does not work that way. Instead, a half-fit ear plug is often providing 0 dB of attenuation.

It simply isn’t true. An ear plug just sitting in the bowl of the outer ear, without sealing the ear canal, is simply nice ear decor — but it is offering little protection from noise. In fact, attenuation measurements show that a poorly-fit ear plug often creates a resonance cavity in the ear canal, actually increasing the noise level by a few decibels (similar to cupping your hand around your ear to hear better).

Assuming that proper use of hearing protection is fairly intuitive (“just put it in your ear...”), many safety managers provide little or no training in how to use protection properly. Or they generously assume that workers will read the manufacturer’s instructions on the packaging.

Any good proof is based upon assumptions: if the assumptions are good, the proof is valid. If the assumptions are bad, then the proof is worthless, or as writer Angelo Donghia puts it, “Assumption is the mother of screw-up.*”

A fourth valuable tool in motivating workers to use Hearing Protection properly is the immediate feedback that comes from fit testing. Tools like VeriPRO® ear plug fit testing or QuietDose™ in-ear dosimetry give workers immediate feedback as to whether they're using that Hearing Protection the right way.

A third tool that we can use to motivate workers is simply to remove barriers to using their hearing protection.

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