Thursday 16 June 2016

Hearing aids

A hearing aid or deaf aid is a device designed to improve hearing. Hearing aids
are classified as medical devices in most countries, and regulated by the respective regulations. Small audio amplifiers such as PSAPs or other plain sound reinforcing systems cannot be sold as "hearing aids".

Earlier devices, such as ear trumpets or ear horns, were passive amplification cones designed to gather sound energy and direct it into the ear canal. Modern devices are computerised electroacoustic systems that transform environmental sound to make it more intelligible or comfortable, according to audiometrical and cognitive rules. Such sound processing can be considerable, such as highlighting a spatial region, shifting frequencies, cancelling noise and wind, or highlighting voice.

Modern hearing aids require configuration to match the hearing loss, physical features, and lifestyle of the wearer. This process is called "fitting" and is performed by audiologists. The amount of benefit a hearing aid delivers depends in large part on the quality of its fitting. Devices similar to hearing aids include the bone anchored hearing aid, and cochlear implant.

Hearing aids are incapable of truly correcting a hearing loss; they are an aid to make sounds more accessible. Two primary issues minimize the effectiveness of hearing aids:

When the primary auditory cortex does not receive regular stimulation, this part of the brain loses cells which process sound. Cell loss increases as the degree of hearing loss increases.
Damage to the hair cells of the inner ear results in sensorineural hearing loss, which affects the ability to discriminate between sounds. This often manifests as a decreased ability to understand speech, and simply amplifying speech (as a hearing aid does) is often insufficient to improve speech perception

During the late 1950s through 1970s, before in-the-ear aids became common (and in an era when thick-rimmed eyeglasses were popular), people who wore both glasses and hearing aids frequently chose a type of hearing aid that was built into the temple pieces of the spectacles. However, the combination of glasses and hearing aids was inflexible: the range of frame styles was limited, and the user had to wear both hearing aids and glasses at once or wear neither. Today, people who use both glasses and hearing aids can use in-the-ear types, or rest a BTE neatly alongside the arm of the glasses. There are still some specialized situations where hearing aids built into the frame of eyeglasses can be useful, such as when a person has hearing loss mainly in one ear: sound from a microphone on the "bad" side can be sent through the frame to the side with better hearing.

This can also be achieved by using CROS or bi-CROS style hearing aids, which are now wireless in sending sound to the better side.

Recent hearing aids include wireless hearing aids. One hearing aid can transmit to the other side so that pressing one aid's program button simultaneously changes the other aid, so that both aids change background settings simultaneously. FM listening systems are now emerging with wireless receivers integrated with the use of hearing aids. A separate wireless microphone can be given to a partner to wear in a restaurant, in the car, during leisure time, in the shopping mall, at lectures, or during religious services. The voice is transmitted wirelessly to the hearing aids eliminating the effects of distance and background noise. FM systems have shown to give the best speech understanding in noise of all available technologies. FM systems can also be hooked up to a TV or a stereo.

2.4 gigahertz Bluetooth connectivity is the most recent innovation in wireless interfacing for hearing instruments to audio sources such as TV streamers or Bluetooth enabled mobile phones. Current hearing aids generally do not stream directly via Bluetooth but rather do so through a secondary streaming device (usually worn around the neck or in a pocket), this bluetooth enabled secondary device then streams wirelessly to the hearing aid but can only do so over a short distance. This technology can be applied to ready-to-wear devices (BTE, Mini BTE, RIE, etc.) or to custom made devices that fit directly into the ear.

Most private healthcare providers in the United States do not provide coverage for hearing aids, so all costs are usually borne by the recipient. The cost for a single hearing aid can vary between $500 and $6,000 or more, depending on the level of technology and whether the clinician bundles fitting fees into the cost of the hearing aid. Though if an adult has a hearing loss which substantially limits major life activities, some state-run vocational rehabilitation programs can provide upwards of full financial assistance. Severe and profound hearing loss often falls within the "substantially limiting" category. Less expensive hearing aids can be found on the internet or mail order catalogs, but most in the under-$200 range tend to amplify the low frequencies of background noise, making it harder to hear the human voice.

Military Veterans receiving VA medical care are eligible for hearing aids based on medical need. The Veterans Administration pays the full cost of testing and hearing aids to qualified military Veterans. Major VA medical facilities provide complete diagnostic and audiology services.

The cost of hearing aids is a tax-deductible medical expense for those who itemize medical deductions.


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