Bad Assumptions About Hearing Protection
- By Brad Witt, MA, CCC-A
- Sep 01, 2008
Put a stop to these. If you don't, they might derail your program.
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.”1
In the world of personal protective equipment, bad assumptions are hazardous and often injurious. Unfortunately, despite 25 years of solid regulation, some persistent bad assumptions are very widespread in Hearing Conservation Programs (HCPs). Here are five of the most common bad assumptions about hearing protection for noise-exposed workers. Perpetuated unchecked, these assumptions torpedo an otherwise healthy Hearing Conservation Program and leave the door open for hearing loss among workers exposed to hazardous noise.
Assumption 1: Hearing protection is self-explanatory.
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.
A comprehensive study of HCPs in the United Kingdom revealed that when hearing conservation training had been provided by posters or leaflets, fewer than half of the “trained” workers could recall the content.2 But repeated studies show that the most effective use of hearing protection comes after one-on-one training. Large group training in hearing protection seems to have little effect on proper usage; only individual training can be linked to high attenuation results.
For proper fit of ear plugs, the fitting steps are not complicated. A simple, three step process conveys the essence of a proper fit for foam ear plugs: Roll, Pull, Hold. Roll down a foam ear plug into a small, crease-free cylinder, pull the outer ear up and back to open the ear canal, insert the ear plug, and hold in place while it expands. The Roll/Pull/Hold mnemonic is illustrated in a NIOSH Web site3 that includes graphics as well as a downloadable video you can use in your own training program.
For proper fit of ear muffs, move aside any thick hair and seat the ear muff so that it encloses the entire ear. Avoid safety glasses with thick temple bars at the frames because they create gaps in the seal that reduce attenuation by 5-10 dB for many ear muffs (see “Earmuffs & Safety Eyewear,”4 a technical bulletin posted on the Howard Leight Web site).
Assumption 2: Any ear plug in the ear is blocking some noise.
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 décor—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 that actually increases the noise level by a few decibels (similar to cupping your hand around your ear to hear better).
This is problematic for a safety manager who is trying to judge compliance visually. He/she might assume that any ear plug that can be seen in a worker’s ear must be doing some good, then focus more on the workers who are wearing no protection at all. In reality, ear plugs that can be seen (from the front) are poorly fit and offer little protection, just like the worker with no ear plug.
Here is one visual cue of a proper ear plug fit: When viewing yourself in a mirror straight ahead (or when looking at a coworker face-to-face), a poorly fit ear plug is clearly visible protruding from the ear canal, while a properly fit ear plug is hardly visible.
For the user, a good self-test of proper fit of ear plugs is easily performed. Prior to inserting your ear plugs, press the palms of your hands tightly against your ears and say some words out loud. Your own voice sounds louder and deeper when your ears are covered. Now, insert your ear plugs and repeat that voice check. If the ear plugs are properly fit, there will be very little difference in the sound of your voice when you cover and uncover your ears with your hands.
Assumption 3: An ear plug halfway in the ear blocks about half the noise.
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.
Workers in noise levels of 85-95 dB (close to the OSHA Permissible Exposure Limit of 90 dB time-weighted average) are routinely offered ear plugs with Noise Reduction Ratings of 30 dB or more. When worn properly, that 30 dB hearing protector can make the worker feel isolated—unable to hear warning signals, co-workers, machine maintenance sounds, or communication radios.
This article originally appeared in the September 2008 issue of Occupational Health & Safety.