An earplug is a device that is inserted in the ear canal to protect the user's ears from loud noises, intrusion of water, foreign bodies, dust or excessive wind. Earplugs may also be used to improve sleep quality or focus in noisy environments. Since they reduce the sound volume, earplugs may prevent hearing loss and tinnitus (ringing of the ears) in some cases.
The US Occupational Safety and Health Administration requires hearing conservation programs, which include the provision of hearing protection devices (HPDs).
History The first recorded mention of the use of earplugs is in the Greek tale Odyssey, wherein Odysseus's crew is warned about the Sirens that sing from an island they will sail past. Circe, 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 company Ohropax, which would produce mainly wax earplugs, was started by the German inventor Max Negwer. He did not invent anything, he just dropped cotton in melted wax and let it dry. 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 earplugs, made from either polyvinyl chloride or polyurethane.
Hearing protection
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), 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 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.
Noise attenuation can be verified using real-ear attenuation at threshold (REAT) or microphone in the real ear (MIRE) methods. The difference in thresholds with and without the hearing protection in place determines the amount of attenuation (REAT). Two microphones measure the sound pressure (of test signals, or noise in the workplace during a shift) outside the HPD and inside, and the difference shows the noise attenuation (MIRE).
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, Honeywell Howard Leight VeriPRO, 3MEARFit and many others.
Noise, dBA Time reaching maximum daily dose, hours : minutes OSHA,
TWA 90 dB(A),
exchange rate 5 dB NIOSH,
TWA 85 dB(A),
exchange rate 3 dB ISO 1999, Netherlands, RF
TWA 80 dB(A),
exchange rate 3 dB 80 - - 8 : 00 81 - 20 : 9.5 6 : 21 82 - 16 : 00 6 : 02 83 21 : 07 12 : 42 4 : 00 84 18 : 23 10 : 4.8 3 : 10 85 16 : 00 8 : 00 2 : 31 86 13 : 56 6 : 21 2 : 00 87 12 : 08 5 : 2.4 1 : 35 88 10 : 33 4 : 00 1 : 16 89 9 : 11 3 : 10 1 : 00 90 8 : 00 2 : 31 48 min 91 6 : 58 2 : 00 38 m 92 6 : 04 1 : 35 30 m 93 5 : 17 1 : 16 24 m 94 4 : 36 1 : 00 19 m 95 4 : 00 0 : 48 15 m 96 3 : 29 0 : 38 12 m 97 3 : 02 0 : 30 9.4 m 98 2 : 38 0 : 24 7.5 m 99 2 : 18 0 : 19 6 m 100 2 : 00 0 : 15 4 m 43 sec 101 1 : 44 0 : 12 3 m 45 s 102 1 : 31 9 min 24 sec 2 m 58 s 103 1 : 19 7 m 30 s 2 m 22 s 104 1 : 09 6 m 1 m 53 s 105 1 : 00 4 m 42 s 1 m 29 s 106 52 m 3 m 48 s 1 m 11 s 107 45 m 3 m 56 s 108 40 m 2 m 24 s 45 s 109 34 m 1 m 54 s 36 s 110 30 m 1 m 30 s 28 s Permissible noise levels in different countries Country TWA, dBA
(for an 8-hour shift) Level increase corresponding to doubling the dose
(Exchange rate) Argentina 90 3 Australia 85 3 Brazil 85 5 Canada 85 & 82 3 Chile 85 5 China 70-90 3 European Union countries 85 3 Finland 85 3 France 85 3 Germany 85, 70, 55For mental work 3 Hungary 85 3 India 90 - Israel 85 5 Italy 85 3 Netherlands 80 3 New Zealand 85 3 Norway 85, 55, 70 3 RF 80 3 Spain 85 3 Sweden 85 3 United Kingdom 85 3 USA 90 (100)* 5 Uruguay 90 3 OSHA issued a directive to the Compliance Safety and Health Officers in 1983. They are ordered to stop requiring employers to install engineering noise control if noise dose < 100 dBA. This decision is considered illegal, Commissioner Cleary's view but it is carried out in practice in most US states.Appendix H. Economic Feasiblity Analysis of Noise Engineering Controls
These numerical values do not fully reflect the real situation. For example, the OSHA standard sets the Action Level 85 dBA, and the PEL 90 dBA. But in practice, the Compliance Safety and Health Officer must record the excess of these values with a margin, in order to take into account the potential measurement error. And, in fact, instead of PEL 90 dBA, it turns out 92 dBA, and instead of AL 85 dBA - 87 dBA.B.9 Extended Workshifts
Types and use cases The diameter of the ear canals can be from 3 to 14 mm. They can be round, elliptical, and even slit-like. The ear canals may be straight, but more often curved to varying degrees. The shape and size of the right and left ear canals for the same worker can vary significantly. Installing the earplugs neatly and tightly (without gaps) can be a difficult task.
Since the fitting of the earplugs greatly affects their noise attenuation, various designs of these personal protective equipment have been developed.
Simple earplugs
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 (MoD) for soldiers to use when firing weapons. Earplugs are rated for their ability to reduce noise; see .
Most disposable earplugs are elastic ones made of memory foam, 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. 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 or silicone.
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 motorcyclists and skiers may also choose to use decibel reduction earplugs to compensate for the ongoing noise of the wind against their head or helmet.
Musician's earplugs
Musicians are exposed to potentially harmful levels of sound, which can lead to hearing loss, 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 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 (frequency spectrum, f.ex. bass and treble levels). These are commonly used by musicians and technicians, both in the studio and in concert, to avoid overexposure to high volume levels. Musicians' earplugs generally achieve a more natural frequency response by incorporating a small diaphragm 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.
Preformed earplugs are universal (non-custom) earplugs with a noise reduction rating (NRR) of about 12 dB. A selection of musicians' earplugs have been reviewed by the National Acoustic Laboratories and The HEARing CRC in conjunction with Choice.National Acoustic Laboratories The review results (which include attenuation measures and user ratings of comfort, fit and sound quality) are available at What Plug?.What Plug?
A more expensive option is the custom molded musicians' 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 engineers who are able to 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.