![Types of Earplugs](https://upload.wikimedia.org/wikipedia/commons/c/c1/Types_of_Earplugs.jpg)
An earplug is a device that is inserted in the
ear canal
The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the pinna to the eardrum and is about in length and in diameter.
Struc ...
to protect the user's ears from loud noises, intrusion of water, foreign bodies,
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
or excessive
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
. Since they reduce the sound volume, earplugs are often used to help prevent
hearing loss
Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Language ...
and
tinnitus
Tinnitus is the perception of sound when no corresponding external sound is present. Nearly everyone experiences a faint "normal tinnitus" in a completely quiet room; but it is of concern only if it is bothersome, interferes with normal hearin ...
(ringing of the ears).
History
The first recorded mention of the use of earplugs is in the Greek tale ''
Odyssey
The ''Odyssey'' (; grc, Ὀδύσσεια, Odýsseia, ) is one of two major Ancient Greek literature, ancient Greek Epic poetry, epic poems attributed to Homer. It is one of the oldest extant works of literature still widely read by moder ...
,'' wherein
Odysseus
Odysseus ( ; grc-gre, Ὀδυσσεύς, Ὀδυσεύς, OdysseúsOdyseús, ), also known by the Latin variant Ulysses ( , ; lat, UlyssesUlixes), is a legendary Greek king of Ithaca and the hero of Homer's epic poem the ''Odyssey''. Odysse ...
's crew is warned about the
Sirens
Siren or sirens may refer to:
Common meanings
* Siren (alarm), a loud acoustic alarm used to alert people to emergencies
* Siren (mythology), an enchanting but dangerous monster in Greek mythology
Places
* Siren (town), Wisconsin
* Siren, Wisco ...
that sing from an island they will sail past.
Circe
Circe (; grc, , ) is an Magician (paranormal), enchantress and a minor goddess in ancient Greek mythology and Ancient Greek religion, religion. She is either a daughter of the Titans, Titan Helios and the Oceanid nymph Perse (mythology), Perse ...
, their hostess, tells them of the Sirens' bewitching song that makes men drive their boats ashore and perish. She advised Odysseus to fashion earplugs for his men from beeswax so they would not be lured to their deaths by the sirens' song.
In 1907, the
German
German(s) may refer to:
* Germany (of or related to)
**Germania (historical use)
* Germans, citizens of Germany, people of German ancestry, or native speakers of the German language
** For citizens of Germany, see also German nationality law
**Ger ...
company Ohropax, which would produce mainly wax earplugs, was started by the German inventor Max Negwer. Ray and Cecilia Benner invented the first moldable pure silicone ear plug in 1962. These earplugs were valued by swimmers because of their waterproof qualities, as well as those trying to avoid harmful noise. Ray Benner, who was a Classical musician, bought McKeon Products in 1962. At that time, the company's sole product was Mack's Earplugs (named after the original owner), which was a moldable clay earplug. The Benners quickly redesigned the product to a silicone version, which would become known as Mack's Pillow Soft Earplugs.
Present-day earplug material was discovered in 1967, at
National Research Corporation (NRC) in the US by Ross Gardner Jr. and his team. As part of a project on sealing joints, they developed a resin with energy absorption properties. They came to call this material "E-A-R" (Energy Absorption Resin). In 1972 the material was refined into commercial
memory foam
Memory foam consists mainly of polyurethane with additional chemicals that increase its viscosity and density. It is often referred to as "viscoelastic" polyurethane foam, or low-resilience polyurethane foam (LRPu). The foam bubbles or ‘cells’ ...
earplugs, made from either polyvinyl chloride or polyurethane.
Hearing protection
![Earplug fitting](https://upload.wikimedia.org/wikipedia/commons/3/3a/Earplug_fitting.png)
There are mainly four types of earplug fittings for hearing protection:
* Foam earplugs, mainly made from either polyvinyl chloride (PVC) or polyurethane (PU) (
memory foam
Memory foam consists mainly of polyurethane with additional chemicals that increase its viscosity and density. It is often referred to as "viscoelastic" polyurethane foam, or low-resilience polyurethane foam (LRPu). The foam bubbles or ‘cells’ ...
), which are compressed (rolled) and put into the ear canal, where they expand to plug it.
* Wax earplugs, which are rolled into a ball and carefully molded to fit over the external portion of the ear canal.
* Flanged silicone earplugs, an example of Universal-fit.
* Custom molded earplugs, made from a mold of the wearer's ear and designed to precisely fit all ear canal shapes. Custom molded is further divided into laboratory-made and "formed in place".
NIOSH
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
Mining Safety and Health Research recommends using the roll, pull, and hold method when using memory foam earplugs.
The process involves the user rolling the earplug into a thin rod, pulling back on the ear, and holding the earplug deep in the ear canal with the finger.
To get a complete seal, the user must wait about 20 to 30 seconds for the earplug to expand inside the canal.
Earplugs are most effective when the wearer has been properly trained on use and insertion. Employers can provide this training before dispensing earplugs to their employees. Training for earplug use includes: insertion, a seal check, depth check, removal, cleaning, and replacement. When training on insertion, the objective is for the worker to understand the correct insertion strategy. Proper insertion training prevents inadequate insertion, that can result in discomfort or inadequate attenuation, which can result in hearing loss. When this step is achieved, then the seal and depth need to be checked. The ear plugs all have a desired depth and seal which need to be achieved to provide the designated attenuation for the wearer. The worker will also be trained on how to properly remove the earplugs and clean them. This allows for multiple uses and reduces the chance of infection. To further prevent infection, it is important the worker understands when they will need to replace their earplugs. Once the plugs have been worn down from repeated use, they will no longer seal correctly or provide the proper attenuation level, and the device will need to be replaced.
Earplugs and other hearing protection devices can be tested to ensure that they fit properly and are successfully limiting sound exposure, which is called
fit-testing. There are a number of different fit-testing systems, also known as field attenuation estimation systems (FAES). These use large headphones or specialized (surrogate) earplugs to transmit the test sounds and measure the attenuation provided by the hearing protector. These systems include the NIOSH HPD Well-Fit, as well as the Honeywell Howard Leight VeriPRO and 3MEARFit.
Hearing protection can also be verified using real-ear methods. Real-ear attentuation at threshold (REAT) measurements test how narrowband noises of varying center frequencies are attenuated with and without hearing protection in place. The difference in thresholds with and without the hearing protection in place determines the amount of attenuation.
Earplugs are especially useful to people exposed to excessively noisy devices or environments (80 dB or more).
Types and use cases
Simple earplugs
![Disposable foam earplugs](https://upload.wikimedia.org/wikipedia/commons/b/b8/Disposable_foam_earplugs.jpg)
Basic foam style earplug protection is often worn by industrial workers who work within hearing distance of
loud machinery for long periods of time, and is used by the British
Ministry of Defence
{{unsourced, date=February 2021
A ministry of defence or defense (see spelling differences), also known as a department of defence or defense, is an often-used name for the part of a government responsible for matters of defence, found in states ...
(MoD) for
soldier
A soldier is a person who is a member of an army. A soldier can be a conscripted or volunteer enlisted person, a non-commissioned officer, or an officer.
Etymology
The word ''soldier'' derives from the Middle English word , from Old French ...
s to use when firing weapons. Earplugs are rated for their ability to reduce noise; see .
![Musicians orange plugs](https://upload.wikimedia.org/wikipedia/commons/b/bf/Musicians_orange_plugs.jpg)
Most disposable earplugs are elastic ones made of
memory foam
Memory foam consists mainly of polyurethane with additional chemicals that increase its viscosity and density. It is often referred to as "viscoelastic" polyurethane foam, or low-resilience polyurethane foam (LRPu). The foam bubbles or ‘cells’ ...
, that is typically rolled into a tightly compressed cylinder (without creases) by the user's fingers and then inserted in the ear canal. Once released, the earplug expands until it seals the canal, blocking the sound vibrations that could reach the
eardrum
In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear
The outer ear, external ear, or auris externa is the extern ...
. Other disposable plugs simply push into the ear canal without being rolled first. Sometimes earplugs are connected with a cord to keep them together when not in use. Other common material bases for disposable earplugs are viscous
wax
Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give low ...
or
silicone
A silicone or polysiloxane is a polymer made up of siloxane (−R2Si−O−SiR2−, where R = organic group). They are typically colorless oils or rubber-like substances. Silicones are used in sealants, adhesives, lubricants, medicine, cooking ...
.
Other devices that provide hearing protection include electronic devices worn around and/or in the ear, and are designed to cancel out the loud noise of a gunshot, while possibly amplifying quieter sounds to normal levels. While rich in features, these electronic devices are more expensive, compared to their foam counterparts.
In other activities, hobby
motorcyclist
Motorcycling is the act of riding a motorcycle. For some people, motorcycling may be the only affordable form of individual motorized transportation, and small-engine displacement, displacement motorcycles are the most common motor vehicle in ...
s and
skier
Skiing is the use of skis to glide on snow. Variations of purpose include basic transport, a recreational activity, or a competitive winter sport. Many types of competitive skiing events are recognized by the International Olympic Committee (IO ...
s may also choose to use decibel reduction earplugs, to compensate for the ongoing noise of the wind against their head or helmet.
Musicians' earplugs
![Musicians earplugs](https://upload.wikimedia.org/wikipedia/commons/8/8e/Musicians_earplugs.jpg)
Musicians are exposed to potentially harmful levels of sound, which can lead to
hearing loss
Hearing loss is a partial or total inability to Hearing, hear. Hearing loss may be present at birth or acquired at any time afterwards. Hearing loss may occur in one or both ears. In children, hearing problems can affect the ability to Language ...
, tinnitus, and other auditory symptoms. Because of this, musicians may choose to use earplugs.
Musician's earplugs (also called Hi-Fi or Lossless earplugs) are designed to
attenuate
In physics, attenuation (in some contexts, extinction) is the gradual loss of flux intensity through a medium. For instance, dark glasses attenuate sunlight, lead attenuates X-rays, and water and air attenuate both light and sound at variable a ...
sounds evenly across all frequencies (pitches) which helps maintain the ear's natural frequency response and thus minimizes the effect on the user's perception of
timbre
In music, timbre ( ), also known as tone color or tone quality (from psychoacoustics), is the perceived sound quality of a musical note, sound or musical tone, tone. Timbre distinguishes different types of sound production, such as choir voice ...
(frequency spectrum, f.ex.
bass and
treble
Treble may refer to:
In music:
*Treble (sound), tones of high frequency or range, the counterpart of bass
*Treble voice, a choirboy or choirgirl singing in the soprano range
*Treble (musical group), a three-piece girl group from the Netherlands
*T ...
levels). These are commonly used by musicians and technicians, both in the studio and in concert, to avoid overexposure to high volume levels. Musician's earplugs generally achieve a more natural frequency response by incorporating a small
diaphragm
Diaphragm may refer to:
Anatomy
* Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen
* Pelvic diaphragm or pelvic floor, a pelvic structure
* Urogenital diaphragm or triangular ligament, a pelvic structure
Other
* Diap ...
or membrane together with acoustic channels and damping materials.
Simpler variants with only a small hole introduce a low frequency leak, and will not achieve a flat frequency response. Examples of manufacturers of membrane-based earplugs are ACS, Etymotic and
Minuendo
Minuendo is a manufacturer of Hearing protection devices in the form of lossless Earplugs for the HSE and hearing health market. The products typically address users that are reliant on sound fidelity and spatial awareness while exposed to stre ...
.
Preformed earplugs, such as the ER-20 earplug are universal (non-custom) earplugs with a noise reduction rating (NRR) of about 12 dB. A selection of musician's earplugs have been reviewed by the National Acoustic Laboratories and The HEARing CRC in conjunction with
Choice
A choice is the range of different things from which a being can choose. The arrival at a choice may incorporate motivators and models. For example, a traveler might choose a route for a journey based on the preference of arriving at a giv ...
. The review results (which include attenuation measures and user ratings of comfort, fit and sound quality) are available at What Plug?.
A more expensive option is the
custom molded musician's earplug, which is custom-made for the individual listener. These earplugs are typically made out of silicone or vinyl materials and come with a vent and a variety of filters that can change the amount of attenuation provided. Common static filter attenuation levels are 9, 15, and 25 dB.
This type of plug is quite popular among
audio engineer
An audio engineer (also known as a sound engineer or recording engineer) helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduction, ...
s who can safely listen to loud mixes for extended periods of time. However, they can be quite costly, being intended for constant re-use unlike simple earplugs which are disposable.
![Metalmania 2007 - Sepultura - Derrick Green 01](https://upload.wikimedia.org/wikipedia/commons/0/06/Metalmania_2007_-_Sepultura_-_Derrick_Green_01.jpg)
Alternately, musicians may use
in-ear monitors
In-ear monitors (IEMs) are devices used by musicians, audio engineers and audiophiles to listen to music or to hear a personal mix of vocals and stage instrumentation for live performance or recording studio mixing. They are also used by telev ...
, which are essentially
headphone
Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an au ...
s that also serve as earplugs by attenuating surrounding sound. In order for in-ear monitors to double up as hearing protection, custom earpieces should be used. The process for having custom earpieces made is similar to that of the custom musician's earplug and, similarly, the earpiece will be made of silicone or vinyl. While using an in-ear monitor can help protect hearing, the amount of protection provided by the monitor depends on the listening level that the musician chooses. Because of this, if the musician sets the monitor to a high level, the monitor may attenuate surrounding sound while still providing a potentially harmful level of sound directly to the musician's ear and therefore no longer serve a protective function.
Several earplugs on the market claim to be for musicians, but are not in fact by definition a musician's earplug. By having a thin acoustical bypass channel, they allow for a slightly better frequency response and lower attenuation than simple earplugs, but far from the level of fidelity that membrane-based earplugs provide. These types of earplugs do not provide the flat attenuation that is characteristic of a musician's plug, but may still be useful for some, due to their lower price points.
Custom molds
Earplugs can be molded to fit an individual's ear canal. This costs more, but can improve fit for the few percent that have an ear anatomy outside the norm.
Custom molded earplugs fall into two categories: Laboratory made and Formed in Place. Laboratory made requires an impression to be made by a professional of the ear canal and outer ear. The impression is sent to a laboratory to be checked and made into a hearing protector. Formed in place uses the same process to make an impression of the ear canal and outer ear and then turns that impression into the protector. Both types of custom molded earplugs are non-disposable with the laboratory made typically lasting for 3 – 5 years and the formed in place lasting for 1 – 2 years.
For the best attenuation and proper fit, the impressions for custom molds must meet a desired criteria by the manufacturer of the mold. Before an impression can be taken for the custom mold the ear canal is checked for any wax or physical abnormalities. This is important in making sure there is a proper seal with the impression material and also not to push any wax deep into the canal. The otoblock (made with foam or cotton) will be inserted deep in the canal to prevent the impression material from going too far. The impression material (either silicone or powder/liquid) will be placed into the ear canal. This will need to be fully made, making sure there are no gaps or creases in the impression. If there are, then the mold made from the impression will not adequately seal the ear canal. Once the custom mold is made, it will need to be inspected by the Audiologist for proper fit on the patient. Hearing protection should also be verified using real-ear methods to ensure proper attenuation. Real-ear attentuation at threshold (REAT) measurements test how narrowband noises of varying frequency are attenuated with and without the custom mold in place. Testing for low-frequency attenuation can help to verify the earmold fit while testing high-frequency attenuation can verify the properties of the filter used.
For best results they are molded in the ear while in the position that they will be used. For instance, if they are to be used for sleeping then they should be molded in the ear while lying down, as different positioning of the jaws causes significant changes to the form of the ear canal, mostly a reduction of the diameter, risking the sleep earplug to be made too large otherwise. It is also important that during the impression process that a music performer use their
embouchure
Embouchure () or lipping is the use of the lips, facial muscles, tongue, and teeth in playing a wind instrument. This includes shaping the lips to the mouthpiece of a woodwind instrument or the mouthpiece of a brass instrument. The word is of ...
or move the jaw to mimic singing in order to account for ear canal changes during performance. Therefore, if the impression is not properly constructed, then it will need to be redone.
These changes can be felt by feeling with a finger just at the entrance to the ear canal while moving the jaws sideways, up and down or
anterior and posterior
Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
.
Most molded earplugs are made from silicone but other materials may be used, including thermoplastics,
plastic, nylon
and even 3-D printed earplugs.
Electronic earplugs
The noise reduction of passive earplugs varies with frequency but is largely independent of level (soft noises are reduced as much as loud noises). As a result, while loud noises are reduced in level, protecting hearing, it can be difficult to hear low level noises. Active electronic earplugs exist, where loud noises are reduced more than soft noises, and soft sounds may even be amplified, providing
dynamic range compression
Dynamic range compression (DRC) or simply compression is an audio signal processing operation that reduces the volume of loud sounds or amplifies quiet sounds, thus reducing or ''compressing'' an audio signal's dynamic range. Compression is ...
. This is done by having a standard passive earplug, together with a microphone/speaker pair (microphone on outside, speaker on inside; formally a pair of
transducer
A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another.
Transducers are often employed at the boundaries of automation, measurement, and contr ...
s), so sound can be transmitted without being attenuated by the earplug. When external sounds exceed an established threshold (typically 82 dBA SPL), the amplification of the electronic circuit is reduced. At very high levels, the amplification is turned off automatically and you receive the full attenuation of the earplug just as if it were turned off and seated in the ear canal. This protects hearing, but allows one to hear normally when sounds are in safe ranges – for example, have a normal conversation in a low-noise situation, but be protected from sudden loud noises, for example at a construction site or a while hunting.
Nonlinear earplugs
Nonlinear earplugs provide similar advantages to electronic earplugs but do not require electricity. They are designed with a thin diaphragm which allows the amount of noise reduction to increase in proportion to the sound level to which the wearer is exposed. This makes them useful for applications where situational awareness is required but noise protection is also necessary, such as the military or police.
Sleep
Earplugs for sleeping are made to be as comfortable as possible while blocking external sounds that may prevent or disrupt sleep. Specialized earplugs for such noises as a partner's
snoring
Snoring is the vibration of respiratory structures and the resulting sound due to obstructed air movement during breathing while sleeping. The sound may be soft or loud and unpleasant. Snoring during sleep may be a sign, or first alarm, of obs ...
may have sound-dampening enhancements that enable the user to still hear other noises, such as an alarm clock.
[Alpine](_blank)
- Sleepsoft earplugs
To determine the comfort of earplugs used for sleeping, it is important to try them on while actually lying down. The pressure on the ear between the head and pillow may cause significant discomfort. Furthermore, just tilting the head back or to the side causes significant anatomical changes in the ear canal, mostly a reduction of the ear canal diameter, which may reduce comfort if the earplug is too large. Earplugs for sleeping may enhance recovery after major surgery.
Protection from water
Some earplugs are primarily designed to keep water out of the ear canal, especially during swimming and water sports. This type of earplug may be made of wax or moldable silicone which is custom-fitted to the ear canal by the wearer.
Exostosis, or
surfer's ear
Surfer's ear is the common name for an exostosis or abnormal bone growth within the ear canal. Surfer's ear is not the same as swimmer's ear, although infection can result as a side effect.
Irritation from cold wind and water exposure causes the ...
, is a condition which affects people who spend large amounts of time in water in cold climates. In addition, wind may increase the prevalence of the amount of exostosis seen in one ear versus the other dependent on the direction it originates from and the orientation of the individual to the wind.
Custom-fitted surfer's earplugs help reduce the amount of cold water and wind that is allowed to enter the external ear canal and, thus, help slow the progression of exostosis.
Another condition is
otitis externa
Otitis externa, also called swimmer's ear, is inflammation of the ear canal. It often presents with ear pain, swelling of the ear canal, and occasionally decreased hearing. Typically there is pain with movement of the outer ear. A high fever is ...
, which is an infection of the outer ear canal. This form of infection differs from those commonly occurring in children behind the eardrum, which is otitis media, or a middle ear infection. This infection's symptoms include: itchiness, redness, swelling, pain upon tugging of the pinna, or drainage. To protect from this form of infection, it is important to thoroughly dry the ears after exposing them to water with a towel. To protect the ears during exposure, the individual can use a head cap, ear plugs, or custom-fitted swim molds.
A 2003 study published in ''Clinical Otolaryngology'' found that a cotton ball saturated with petroleum jelly was more effective at keeping water out of the ear, was easier to use, and was more comfortable than wax plugs, foam plugs, EarGuard, or Aquafit.
Jacques-Yves Cousteau
Jacques-Yves Cousteau, (, also , ; 11 June 191025 June 1997) was a French naval officer, oceanographer, filmmaker and author. He co-invented the first successful Aqua-Lung, open-circuit SCUBA (self-contained underwater breathing apparatus). Th ...
warned that earplugs are harmful to divers, especially
scuba divers
This is a list of underwater divers whose exploits have made them notable.
Underwater divers are people who take part in underwater diving activities – Underwater diving is practiced as part of an occupation, or for recreation, where t ...
. Scuba divers breathe compressed
air
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...
or other gas mixtures at a pressure matching the water pressure. This pressure is also inside the ear, but not between the eardrum and the earplug, so the pressure behind the eardrum will often burst the eardrum. Skin divers have less pressure inside the ears, but they also have only atmospheric pressure in the outer ear canal. The PADI (Professional Association of Diving Instructors) advises in the "Open Water Diver Manual" that only vented earplugs designed for diving should be used in diving.
Flight ear protection
Earplugs are also available which help to protect ears from the pain caused by airplane cabin pressure changes. Some products contain a porous ceramic insert which reportedly aids equalization of air pressure between the middle and outer ear thereby preventing pain during landings and take-offs. Some airlines distribute regular foam earplugs as part of their amenity kits for passengers to aid their comfort during landings and takeoffs as well as to reduce exposure to the aircraft's noise during the flight. These can help passengers get to sleep during the flight if desired.
Rating
The
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
(EPA) mandates that hearing protection is rated and labeled. To be rated, hearing protection is tested under ANSI S3.19-1974 to provide a range of attenuation values at each frequency that can then be used to calculate a Noise Reduction Rating (NRR). Under this standard a panel of ten subjects are tested three times each in a laboratory to determine the attenuation over a range of 9 frequencies.
In the European Union, hearing protectors are required to be tested according to the International Organization for Standardization (ISO) acoustical testing standard, ISO 4869 Part 1 and the Single Number Rating (SNR) or High/Middle/Low (HML) ratings are calculated according to ISO 4869 Part 2. In Brazil, hearing protectors are tested according to the American National Standards Institute ANSI S12.6-1997 and are rated using the Noise Reduction Rating Subject Fit NRR(SF). Australia and New Zealand have different standards for protector ratings yielding a quantity SLC80 (Sound Level Class for the 80th percentile). Canada implements a class system for rating the performance of protectors. Gauger and Berger have reviewed the merits of several different rating methods and developed a rating system that is the basis of a new American National Standard, ANSI S12.68-2007
The various methods have slightly different interpretations, but each method has a percentile associated with the rating. That percent of the users should be able to achieve the rated attenuation. For instance, the NRR is determined by the mean attenuation minus two standard deviations. Thus, it translates to a 98% statistic. That is, at least 98 percent of users should be able to achieve that level of attenuation. The SNR and HML are a mean minus one standard deviation statistic. Therefore, approximately 86% of the users should be able to achieve that level of protection. Similarly, the NRR (SF) is a mean minus one standard deviation and represents an 86% of users should achieve that level of protection. The difference between the ratings lies in how the protectors are tested. NRR is tested with an experimenter-fit protocol. SNR/HML are tested with an experienced subject-fit protocol. NRR (SF) is tested with a naive subject-fit protocol. According to Murphy, et al. (2004), these three protocols will yield different amounts of attenuation with the NRR being the greatest and NRR (SF) being the least.
The experimenter-fit NRR should be adjusted per the guidelines of the National Institute for Occupational Safety and Health as the required NRR ratings differ greatly from lab tests to field tests.
The NRR(SF) used in Brazil, Australia, and New Zealand does not require derating as it resembles the manner in which the typical user will wear hearing protection.
Noise Reduction Rating (NRR)
Hearing protectors
Ear protection refers to devices used to protect the ear, either externally from elements such as cold, intrusion by water and other environmental conditions, debris. High levels of exposure to noise may result in noise-induced hearing loss
N ...
sold in the US are required by the EPA to have a noise reduction rating (NRR),
which is an estimate of noise reduction at the ear when protectors are worn properly.
Real-ear attenuation at threshold (REAT) measurements are performed multiple times with 10 to 20 subjects to determine the NRR. Using the collected data, an average group attenuation is reported along with a standard deviation for attenuation on the hearing protector package.
Due to the discrepancy between how protectors are fit in the testing laboratory and how users wear protectors in the real world, the
Occupational Safety and Health Administration
The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
(OSHA) and the
National Institute for Occupational Safety and Health
The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...
(NIOSH) have developed derating formulas to reduce the effective NRR.
While the NRR and the SNR (Single Number Rating) are designed to be used with
C-weighted noise, which means that the lower frequencies are not de-emphasized, other ratings (NRR(SF) and NRSA) are determined for use with A-weighted noise levels, which have lower frequencies de-emphasized. NIOSH recommended and the U.S. EPA mandated
that 7-dB compensation between C and A weighting be applied when the NRR is used with A-weighted noise levels.
The OSHA training manual for inspectors says the adequacy of hearing protection for use in a hazardous noise environment should be derated to account for how workers typically wear protection relative to how manufacturers test the protector's attenuation in the laboratory.
[Occupational Health and Safety Administration, January, 1999. The OSHA Technical Manual, OSHA Publication,]
Section IV, Appendix IV: C.
For all types of hearing protection, OSHA's derating factor is 50%. If used with C-weighted noise, the derated NRR will become NRR/2.
If used with A-weighted noise, OSHA applies the 7-dB adjustment for C-A weighting first then derates the remainder.
For example, a protector with 33-dB attenuation would have this derating:
: Derated NRR = (33 – 7)/2
NIOSH has proposed a different method for derating based upon the type of protector.
[Linda Rosenstock et al. ] For
earmuffs
Earmuffs are clothing accessories or personal protective equipment designed to cover a person's ears for hearing protection or warmth. They consist of a thermoplastic or metal head-band that fits over the top or back of the head, and a cushion o ...
, the NRR should be derated by 25%, for slow-recovery foam earplugs the derating is 50% for all other protection, the derating is 70%. NIOSH applies the C-A spectral compensation differently than OSHA. Where OSHA subtracts the 7-dB factor first and derates the result, NIOSH derates the NRR first and then compensates for the C-A difference. For example, to find the derated NRR for an earmuff by using the NIOSH derating system, the following equation would be used:
: Derated NRR = (Original NRR x (1-.25)) – 7
Painful discomfort occurs at approximately 120 to 125 dB(A), with some references claiming 133 dB(A) for the threshold of pain.
Active
ear muffs
Earmuffs are clothing accessories or personal protective equipment designed to cover a person's ears for Ear protection, hearing protection or warmth. They consist of a plastic, thermoplastic or metal head-band that fits over the top or back of ...
are available with electronic noise cancellation that can reduce direct path ear canal noise by approximately 17–33 dB, depending on the low, medium, or high frequency at which attenuation is measured. Passive earplugs vary in their measured attenuation, ranging from 20 dB to 30 dB, depending on whether they are properly used, and if low pass mechanical filters are also being used.
In practice
Using both ear muffs (whether passive or active) and earplugs simultaneously results in maximum protection, but the efficacy of such combined protection relative to preventing permanent ear damage is inconclusive, with evidence indicating that a combined noise reduction ratio (NRR) of only 36 dB (C-weighted) is the maximum possible using ear muffs and earplugs simultaneously, equating to only a 36 - 7 = 29 dB(A) protection.
Some high-end, passive, custom-molded earplugs also have a mechanical filter inserted into the center of the earmolded plug, with a small opening facing to the outside; this design permits being able to hear range commands at a gun range, for example, while still having full rating impulse noise protection.
Such custom molded earplugs with low pass filter and mechanical valve typically have a +85 dB(A) mechanical clamp, in addition to having a
lowpass filter
A low-pass filter is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. The exact frequency response of the filter depends on the filter des ...
response, thereby providing typically 30-31 dB attenuation to loud impulse noises, with only a 21 dB reduction under low noise conditions across the human voice audible frequency range (300–4000 Hz) (thereby providing low attenuation between shots being fired), to permit hearing range commands. Similar functions are also available in standardized earplugs that are not custom molded.
Expected updates
In 2007, the
American National Standards Institute
The American National Standards Institute (ANSI ) is a private non-profit organization that oversees the development of voluntary consensus standards for products, services, processes, systems, and personnel in the United States. The organi ...
published a new standard for noise reduction ratings for hearing protectors, ANSI S12.68-2007. Using the real ear attenuation at threshold data collected by a laboratory test prescribed in ANSI S12.6-2008, the noise reduction statistic for A-weighted noise (NRSA) is computed using a set of 100 noises listed in the standard.
[ANSI S12.68 (2007). American National Standard Methods of Estimating Effective A-Weighted Sound Pressure Levels When Hearing Protectors, are Worn, American National Standards Institute, New York.] The noise reduction rating, rather than be computed for a single noise spectrum the NRSA incorporates variability of both subject and spectral effects.
ANSI S12.68 also defines a method to estimate the performance of a protector in an atypical noise environment.
Building upon work from the
U.S. Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Signal ...
and the ISO 4869-2 standard,
[ISO 4869-2 (1994). ''Acoustics—Hearing Protectors Part 2: Estimation of effective A-weighted sound pressure levels when hearing protectors are worn,'' International Organization for Standardization, Geneva.] the protector's attenuation as a function of the difference in C and A-weighted noise level is used to predict typical performance in that noise environment. The derating may be quite severe (10 to 15 decibels) for protectors that have significant differences between low and high frequency attenuation. For "flat" attenuation protectors, the effect of C-A is less. This new system eliminates the need for calculators, relies on graphs and databases of empirical data, and is believed to be a more accurate system for determining NRRs.
Personal attenuation rating (PAR)
Similar to a noise reduction rating (NRR) required on hearing protection devices in the United States, a personal attenuation rating (PAR) can be obtained through a
hearing protection fit-testing system.
The PAR is subtracted from the measured noise exposure to estimate the total noise exposure an individual is receiving when wearing hearing protection. The PAR is regarded as more accurate than the NRR because it is calculated per individual and per hearing protection device, while NRR is a generalized estimate of potential sound reduction based on the protection provided to a small population of people.
Health risks
![Man inserting earplugs](https://upload.wikimedia.org/wikipedia/commons/f/fb/Man_inserting_earplugs.jpg)
Earplugs are generally safe, but some precautions may be needed against a number of possible health risks, with additional ones appearing with long-term use:
*Pushing in earplugs into the external ear canal may cause the
air pressure
Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equival ...
to rise in it, in effect pushing against the eardrum and causing pain. This may be caused by pressure on the ear while lying down on the side, and is also the case when completely expanded foam earplugs are pushed further into the ear. To bypass the latter risk, such earplugs are instead removed, compressed and inserted to the desired depth. Vice versa, when pulled out, the resultant
negative pressure
Negative pressure may refer to:
* Negative value of a Pressure#Negative pressures, pressure variable
* Negative room pressure, a ventilation technique used to avoid contaminating outside areas
* Negative pressure ventilator, also known as an iron ...
pulls the eardrum. Therefore, some earplugs are better carefully screwed or jiggled out rather than yanked out. Yawning does not help to equalize this air pressure difference, since it equalizes the pressures between the middle ear and the environment, while this overpressure rather is located in the outer ear, between the eardrum and the earplug.
*If pushed too far into the ear canal, they may push
earwax
Earwax, also known by the medical term cerumen, is a brown, orange, red, yellowish or gray waxy substance secreted in the ear canal of humans and other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, a ...
and debris into the canal and possibly against the ear drum. As a precaution, earplugs should not be pushed further into the ear canal than they may be grabbed and rotated.
Earwax impacted by earplugs can be removed by irrigation or other remedies, as described
here
Here is an adverb that means "in, on, or at this place". It may also refer to:
Software
* Here Technologies, a mapping company
* Here WeGo (formerly Here Maps), a mobile app and map website by Here
Television
* Here TV (formerly "here!"), a TV ...
.
*There is a possibility of
allergic reaction
Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...
s, but this is likely rare, as earplugs generally are made of immunologically inert materials.
Long-term use
Custom shaped plugs are recommended for long-term use, since they are more comfortable and gentle to the skin and won't go too far into the ear canal.
Nevertheless, prolonged or frequently repeated use of earplugs has the following health risks, in addition to the short-term health risks:
*They may cause
earwax
Earwax, also known by the medical term cerumen, is a brown, orange, red, yellowish or gray waxy substance secreted in the ear canal of humans and other mammals. It protects the skin of the human ear canal, assists in cleaning and lubrication, a ...
to build up and plug the
outer ear
The outer ear, external ear, or auris externa is the external part of the ear, which consists of the auricle (also pinna) and the ear canal. It gathers sound energy and focuses it on the eardrum (tympanic membrane).
Structure
Auricle
The ...
, since it blocks the normal flow of earwax outwards.
[NHS Ear Wax Build-up](_blank)
- Ear plugs This can result in tinnitus, hearing loss, discharge, pain or infection.
Excess earwax should be carefully
removed from the ear, and earplugs should be cleaned regularly with water and mild soap. However, foam type earplugs are usually designed to be disposable, and will expand and lose their memory property upon drying after washing with water and soap. From then on, they will expand very quickly after being compressed, making proper insertion into the ear canal quite problematic. They also lose a large proportion of sound attenuating capability after such washing and drying.
*They may cause irritation of the
temporomandibular joint
In anatomy, the temporomandibular joints (TMJ) are the two joints connecting the jawbone to the skull. It is a bilateral synovial articulation between the temporal bone of the skull above and the mandible below; it is from these bones that it ...
, which is located very close to the ear canal, causing pain. Individually fitted non-elastic earplugs may be less likely to cause this irritation compared with foam ones that expand inside the ear canal.
*Earplugs are also a possible cause of ear inflammation (
otitis externa
Otitis externa, also called swimmer's ear, is inflammation of the ear canal. It often presents with ear pain, swelling of the ear canal, and occasionally decreased hearing. Typically there is pain with movement of the outer ear. A high fever is ...
), although the short-term use of earplugs when swimming and shampooing hair may actually help prevent it. Still, many
pathogenic bacteria
Pathogenic bacteria are bacteria that can cause disease. This article focuses on the bacteria that are pathogenic to humans. Most species of bacteria are harmless and are often Probiotic, beneficial but others can cause infectious diseases. The n ...
grow well on warm, moist, foam-type plugs (polyvinylchloride (PVC) or polyurethane). However, there need also be a loss of integrity of the skin for infection to occur. Hard and poorly fitting earplugs can scratch the skin of the ear canal and set off an episode. When earplugs are used during an acute episode, disposable plugs are recommended, or used plugs must be cleaned and dried properly to avoid contaminating the healing ear canal with infected discharge.
See also
*
Noise-induced hearing loss
Noise-induced hearing loss (NIHL) is a Hearing loss, hearing impairment resulting from exposure to loud sound. People may have a loss of perception of a narrow range of Frequency, frequencies or impaired perception of sound including hyperacusi ...
*
Occupational hearing loss
Occupational hearing loss (OHL) is hearing loss that occurs as a result of occupational hazards, such as excessive noise and ototoxic chemicals. Noise is a common workplace hazard, and recognized as the risk factor for noise-induced hearing loss a ...
References
External links
OSHA's letter of interpretation on hearing protection-fit-testingRoyal National Institute for Deaf peopleNational Institute for Occupational Safety and Health - Hearing Protector Device CompendiumNIOSH Science Blog: NIOSH HPD Well-Fit™: The Future is Fit-Testing
{{Competitive swimwear
Protective gear
Noise control
Articles containing video clips
Occupational safety and health
Audiology