Earplug
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 be used as well to improve sleep quality or focus in noisy environments. Since they reduce the sound volume, earplugs may prevent hearing loss and tinnitus, in some cases.
US Occupational Safety and Health Administration requires hearing conservation programs which include the provision of hearing protection devices. But this does not mean that OSHA considers HPDs to be effective.
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. 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, 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 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". 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 or polyurethane , which are compressed 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".
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 or microphone in the real ear methods. The difference in thresholds with and without the hearing protection in place determines the amount of attenuation. Two microphones measure the sound pressure outside the HPD and inside, and the difference shows the noise attenuation.
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. These use large headphones or specialized 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.
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 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 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 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 are designed to attenuate sounds evenly across all frequencies which helps maintain the ear's natural frequency response and thus minimizes the effect on the user's perception of timbre. 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 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.
Preformed earplugs, such as the ER-20 earplug are universal earplugs with a noise reduction rating 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. The review results 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 engineers 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.
File:Metalmania 2007 - Sepultura - Derrick Green 01.jpg|thumb|Lead singer of the metal band Sepultura Derrick Green wearing a custom earplug
Alternately, musicians may use in-ear monitors, which are essentially headphones 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.