Hearing Protection: It's Not Just About Noise Reduction

Hearing protectors add foreign objects to our heads and ears. They can add unwelcome pressure, weight and warmth and interfere with hearing neccessary sounds. When we speak while wearing hearing protectors, our own voices don't sound normal.

Earplugs take it one step further, as they must be inserted into our ear canals. Their invasive nature amplifies our awareness that something foreign is present. Our personal space just is not being shared, it has been violated by something entering within. Earplugs make it personal, and employees wearing them are going to demand (passively or actively) consideration of their needs and preferences.

For years, the hearing conservation mantra was, “The best hearing protection is the one that is worn.” Today, we don't hear this as much and when we do, the word “properly,” is added. Our emphasis on proper use is the result of a plethora of studies that have shown that, as used in the workplace, wearing hearing protection doesn't always equate to effective protection or to laboratory-generated noise reduction ratings (NRRs).¹ Noise reduction, as represented by the Environmental Protection Agency's NRR, just may be the cover on the book.

AVOID OVERPROTECTION

The loudest occupational noise hazards usually come to mind first. The military is a good example of situations that have loud occupational noise. Flight operations on aircraft carriers could be the loudest steady state noise exposures on the planet, approaching 153 dBA. Shoulder-fired rockets are among the loudest and most hazardous impulse noise exposures. The challenges of protecting personnel from these extreme hazardous noise exposures can influence the mindset for the general selection of hearing protection.

The old adage, “If a little will do a little good, then a lot will do a lot of good” doesn't always apply, especially in the case of hearing protection. An exclusive focus on maximum noise reduction can lead to overprotection that isolates the wearer. Paradoxically, overprotection can result in less protection when the user rebels against the imposed isolation or becomes injured as a result of not being able to hear warning sounds.

Standard threshold shifts (STSs) in hearing trigger medical referrals, which often return a blanket recommendation to wear double hearing protection (earplugs and earmuffs in combination), regardless of the noise exposure. When appropriate, the more savvy hearing conservation personnel ignore such recommendations and refit and match the hearing protector to the individual and the noise exposure. Earmuffs purposefully are ranged in NRRs to tailor the level of protection to the noise exposure.

GOT COMFORT?

While acceptance of safety eyewear is influenced by appearance (they'd better be “cool looking”), hearing protection acceptance is more dependent on feel: they'd better feel comfortable. Although a relative term among hearing protection users, comfort probably is the first consideration. Decisions about comfort sometimes are made by feeling the earplug with the fingertips when the user should be testing it in the ear canal.

The use of earbuds with iPods has helped overcome Mother's prohibition of “never sticking anything in your ear smaller than you elbow.” However, a less comfortable acoustic seal with a deeper level of insertion into the ear canal is required for effective hearing protection.

A goal of the hearing protection industry is to design earplugs that are tough on noise (with a high NRR), but easy on the ears. Foam earplugs generally fit this bill.

Most earplugs are designed to limit their depth of insertion to the more flexible outer third of the ear canal, which consists of skin and cartilaginous tissue. Deeper insertion custom-molded earplugs are being proposed for some of the highest level steady state noise environments. The additional noise reduction provided can come at the price of comfort. All earplugs take some getting used to. Few workers, though, may be able to tolerate deep insertion earplugs that extend into a more sensitive area of the ear canal, where a thin layer of skin covers bone.

The cough reflex also becomes an issue the deeper an earplug is inserted into the ear canal. A branch of the 10^th vagas nerve, which lines the ear canal and innervates the larynx (voice box), is thought to be responsible. The cough reflex is more sensitive in some than others and not everyone may be able to adapt and tolerate deep-insertion earplugs.