Glossary: Hearing Protection Devices

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Glossary: Hearing Protection Devices

What's the difference between a single- and multiple-use earplug? Bands vs. earmuffs? This glossary covers basic terms related to Hearing Protection Devices (HPD).


Banded Earplugs

A kind of a hybrid between an earmuff and an earplug, they provide the portability and convenience of earplugs, with the ease of use of earmuffs. The pressure of the band facilitates insertion, and users can just pop them on, walk into a noisy area, then take them off when they exit. Most can be carried in a pocket or hung around the neck. They are also an alternative in hot temperatures where earmuffs can become uncomfortable.



Detectable Earplugs

An optional feature of some earplugs, designed to avoid contamination in food and other process industries. In a metal-detectable earplug, a metal component is added to the earplug and/or cord during production which can be recognized by contamination sensors in the processing line. In a visually-detectable earplug, colorant is used to produce an earplug that is easily detected in contaminant inspections.




Any material that is electrically non-conductive. The term is used to describe the non-conductive feature of some earmuff cups and bands – a safety feature that is particularly useful for industrial wearers who work around live electrical components.



Earplug Fit Testing

Earplug fit-testing can help determine the actual attenuation workers receive from their earplugs, taking much of the guesswork out of the hearing protector selection process. Fit testing provides both safety managers and workers the information they need to select hearing protection based on a PAR for the worker using his or her actual earplugs in their actual work environment. This information helps safety managers determine whether workers are receiving optimal protection, require additional training on how to fit their earplugs, or need to try a different model. Systems, such as VeriPRO® from Howard Leight®, can be used with any model of earplug.

Read more about Earplug Fit Testing in a Best Practices Bulletin issued by the National Hearing Conservation Association / Occupational Safety & Health Administration (U.S.) Alliance.



Hearing Protection Device (HPD)

A generic term for earplugs, earmuffs, and banded protectors.



Multiple-Use Earplug

Also known as reusable earplugs. Multiple-use earplugs are typically molded with a semi-rigid stem and pliable flanges, so they don't require rolling prior to insertion. They insert easily, and can be quite comfortable for extended periods. While they are significantly more expensive than disposable foam earplugs, over time they can actually be more economical. 



Noise Blocking or Passive Earmuff

They block sound using just the foam and other components of the ear cup.



Occlusion Effect

The amplification of body-borne sounds caused when you occlude (close off) the ear canal. This can be demonstrated by singing the vowel sound ‘ee’ while you lightly push your tragus closed (the tragus is that little flap at your ear canal). Most people hear the ‘ee’ become much louder with their ear occluded. The Occlusion Effect contributes to a variety of complaints among hearing protector users: “My voice sounds like I’m in a barrel,” or “My own footsteps are too loud.” It is more noticeable in banded hearing protectors and shallow-insertion earplugs. With hearing protectors, the Occlusion Effect is reduced by inserting the earplug deeper into the ear canal, or by stiffening the soft portion of the ear canal by using an earplug with more surface contact in the ear canal.




Even in noisy environments, there are sounds we want to hear clearly – warning signals and alarms, voices of coworkers, even maintenance sounds from machinery. Just as hearing protectors may not provide enough attenuation, there are many instances where they provide too much attenuation. NIOSH estimates that 90% of noise-exposed workers in the U.S. are exposed to less than 95 dBTWA (meaning they only need about 10 dBof effective attenuation). Workers who are overpro tected say they feel isolated and cut off from their work environment – and not as safe. While there are no U.S. standards defining overprotection, a comparable European guidance document (EN 458) recommends that attenuated noise levels (under hearing protectors) should be no lower than 70-84 dB for ideal communication in noise.



Single-Use Earplug

Single-use, or disposable, earplugs are the most common type used today. They are popular because of their low cost, ease of use, and high level of comfort. There are different styles, ranging from the 35 year-old yellow PVC barrel earplugs to the latest contoured polyurethane (PU) foam earplugs. Single-use earplugs are available in corded or uncorded styles, and can be distribute from dispensers. Corded earplugs are convenient if you have a process that generates noise intermittently—they can be taken out and hung around your neck, then reinserted as needed.



Uniform (or Flat) Attenuation

Conventional hearing protectors inherently attenuate high frequencies more than low frequencies. This produces a muffled and distorted signal when wearing hearing protectors, most noticeable when the incoming signal includes music or speech, not just noise. Hearing protection device designers have overcome some of this high-frequency bias, developing a variety of hearing protectors that attenuate fairly uniformly across all frequencies, a response called uniform attenuation. A hearing protector with uniform attenuation will reduce all incoming noise fairly equally, regardless of frequency. In industrial settings, many users of uniform attenuation HPDs report that speech and conversation sounds more natural when compared with conventional hearing protection.