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A Hearing Aid Is an Electroacoustic Device Which Typically Fits in Or Behind the Wearer's Ear, and Is Designed to Amplify and Modulate Sound for the Wearer

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A Hearing Aid Is an Electroacoustic Device Which Typically Fits in Or Behind the Wearer's Ear, and Is Designed to Amplify and Modulate Sound for the Wearer A hearing aid is an electroacoustic device which typically fits in or behind the wearer's ear, and is designed to amplify and modulate sound for the wearer. Earlier devices, known as ear trumpets or ear horns,[1][2] were passive funnel-like amplification cones designed to gather sound energy and direct it into the ear canal. Similar devices include the bone anchored hearing aid, and cochlear implant. Contents [hide] 1 Types o 1.1 Invisible in canal aids o 1.2 Body worn aids o 1.3 Behind the ear aids (BTE) . 1.3.1 Receiver in the Canal/Ear (CRT/RIC/RITE) . 1.3.2 Earmolds o 1.4 In the ear aids (ITE) o 1.5 Invisible in canal hearing aids (IIC) o 1.6 Extended wear hearing aids o 1.7 Open-fit devices o 1.8 Personal, user, self, or consumer programmable o 1.9 Disposable hearing aids o 1.10 Bone anchored hearing aids (BAHA) o 1.11 Eyeglass aids 2 Technology o 2.1 Compatibility with telephones o 2.2 Wireless hearing aids o 2.3 Directional microphones o 2.4 Telecoil . 2.4.1 Legislation affecting use o 2.5 Direct audio input o 2.6 Processing 3 Indications 4 Adjustment 5 Evaluation 6 Regulation o 6.1 Ireland o 6.2 United States 7 Purchase costs o 7.1 Australia o 7.2 Canada o 7.3 Iceland o 7.4 India o 7.5 UK o 7.6 US 8 Batteries 9 See also 10 References 11 External links [edit]Types There are many types of hearing aids (also known as hearing instruments), which vary in size, power and circuitry. Among the different sizes and models are: NIH illustration of different hearing aid types. [edit]Invisible in canal aids This style of hearing aids fits inside the ear canal completely, leaving little to no trace of an installed hearing aid visible. [edit]Body worn aids This was the first type of hearing aid invented by Harvey Fletcher while working at Bell Laboratories.[3] Body aids consist of a case and an earmold, attached by a wire. The case contains the electronic amplifier components, controls and battery while the earmold typically contains a miniature loudspeaker. The case is typically about the size of a pack ofplaying cards and is carried in a pocket or on a belt.[4] Without the size constraints of smaller hearing devices body worn aid designs can provide large amplification and long battery life at a lower cost. Body aids are still marketed in emerging markets because of their lower cost.[4] [edit]Behind the ear aids (BTE) A pair of BTE hearing aids BTE aids consist of a case, an earmold or dome and a connection between them. The case contains the electronics, controls, battery, microphone(s) and often the loudspeaker. Generally, the case sits behind the pinna with the connection from the case coming down the front into the ear. The sound from the instrument can be routed acoustically or electrically to the ear. If the sound is routed electrically, the speaker (receiver) is located in the earmold or an open-fit dome, while acoustically coupled instruments use a plastic tube to deliver the sound from the case’s loudspeaker to the earmold.[5] BTEs can be used for mild to profound hearing loss. As the electrical components are located outside the ear, the chance of moisture and earwax damaging the components is reduced, which can increase the durability of the instrument. BTEs are also easily connected to assistive listening devices, such as FM systems, to directly integrate sound sources with the instrument. BTE aids are commonly worn by children who need a durable type of hearing aid.[4] "Mini" BTE (or "on-the-ear") aids: A new type of BTE aid called the mini BTE (or "on- the-ear") aid. It also fits behind/on the ear, but is smaller. A very thin, almost invisible tube is used to connect the aid to the ear canal. Mini BTEs may have a comfortable ear piece for insertion ("open fit"), but may also use a traditional earmold. Mini BTEs allow not only reduced occlusion or "plugged up" sensations in the ear canal, but also increase comfort, reduce feedback and address cosmetic concerns for many users.[6] [edit]Receiver in the Canal/Ear (CRT/RIC/RITE) BTE hearing instruments that place the loudspeaker directly in the ear without a fitted earmold are often referred to as “Receiver in the Canal” instruments. These instruments use soft ear inserts, typically of silicone, to position the loudspeaker in the patient’s ear. Some of the advantages with this approach include improved sound quality, reduced case size, “open-fit” technology, and immediate patient fitting.[citation needed] [edit]Earmolds An earmold is created from an impression taken of the individual's outer ear. This usually ensures a comfortable fit and reduces the possibility of feedback.[4] Earmolds are made from a variety of hard (firm) and soft (pliable) materials. The color of the case and earmold of a BTE aid can be modified and optional decorations can be added.[citation needed] [edit]In the ear aids (ITE) These devices fit in the outer ear bowl (called the concha); they are sometimes visible when standing face to face with someone. ITE hearing aids are custom made to fit each individual's ear. They can be used in mild to some severe hearing losses. Feedback, a squealing/whistling caused by sound (particularly high frequency sound) leaking and being amplified again, may be a problem for severe hearing losses.[citation needed] Some modern circuits are able to provide feedback regulation or cancellation to assist with this. Venting may also cause feedback. A vent is a tube primarily placed to offer pressure equalization. However, different vent styles and sizes can be used to influence and prevent feedback. [7] Traditionally, ITEs have not been recommended for young children because their fit could not be as easily modified as the earmold for a BTE, and thus the aid had to be replaced frequently as the child grew.[citation needed]However, there are new ITEs made from a silicone type material that mitigates the need for costly replacements. ITE hearing aids can be connected wirelessly to FM systems, for instance with a body-worn FM receiver with induction neck-loop which transmits the audio signal from the FM transmitter inductively to the telecoil inside the hearing instrument. ITC aids are smaller, filling only the bottom half of the external ear. The aid cannot be seen when face to face with the wearer. MIC and CIC aids are generally not visible unless the viewer looks directly into the wearer's ear.[8][9] These aids are intended for mild to moderately-severe losses. CICs are usually not recommended for people with good low frequency hearing, as the occlusion effect is much more noticeable.[10] In-the-ear hearing aids are typically more expensive than behind-the-ear counterparts of equal functionality, because they are custom fitted to the patient's ear. In fitting, an audiologist takes a physical impression (mold) of the ear. The mold is scanned by a specializedCAD system, resulting in a 3D model of the outer ear. During modeling, the venting tube is inserted. The digitally modeled shell is printed using a rapid prototyping technique such as stereolithography. Finally, the aid is assembled and shipped to the audiologist after a quality check.[11] [edit]Invisible in canal hearing aids (IIC) This type of hearing aid fitting is not visible when worn. This is because it fits deeper in the canal than other types, so that it is out of view even when looking directly into the ear bowl (concha). A comfortable fit is achieved because the shell of the aid is custom-made to the individual ear canal after taking a mould. Invisible hearing aid types use venting and their deep placement in the ear canal to give a more natural experience of hearing. Unlike other hearing aid types, with the IIC aid the majority of the ear is not blocked (occluded) by a large plastic shell. This means that sound can be collected more naturally by the shape of the ear, and can travel down into the ear canal as it would with unassisted hearing. Some models allow the wearer to use a mobile phone as a remote control to alter memory and volume settings, instead of taking the IIC out to do this. IIC types are most suitable for users up to middle age, but are not suitable for more elderly people. [edit]Extended wear hearing aids Main article: Extended wear hearing aid Extended wear hearing aids are hearing devices that are non-surgically placed in the ear canal by a hearing professional. The extended wear hearing aid represents the first "invisible" hearing device. These devices are worn for 1–3 months at a time without removal. They are made of soft material designed to contour to each user and can be used by people with mild to moderately severe hearing loss. Their close proximity to the ear drum results in improved sound directionality and localization, reduced feedback, and improved high frequency gain.[citation needed] While traditional BTE or ITC hearing aids require daily insertion and removal, extended wear hearing aids are worn continuously and then replaced with a new device. Users can change volume and settings without the aid of a hearing professional. The devices are very useful for active individuals because their design protects against moisture and earwax and can be worn while exercising, showering, etc.
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