Facts on Bone Conduction Hearing Aids

Published: 10th February 2009
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The industry providing help to hearing impaired individuals are focused on those with partial or minimal hearing loss. There are several types of hearing aids. One is the Bone Conduction Hearing Aid. It is very much different from the air conduction hearing aid. A conventional one amplifies sound and ushers it through what we call the ear mold, which is protruded from the head, into the ear canal all the way through the inner ear. Passing onto three small bones in the middle ear are vibrations and carries them into the cochlea. Signals in the auditory nerve are generated when the tiny hair cells are affected. Finally, the brain interprets them as the sound we hear. These are much more effective than the bone conduction hearing aids. However, unlike the Bone Conduction/Anchored Hearing Aid, this type is not suitable for children with Atresia, since sound cannot be transmitted because the ear canal is blocked and sound must be transmitted in a different manner.

As a general definition, Bone Conduction amplifies the lower frequencies resulting to most people hearing their own voice in a lower pitch than the normal. The Bone Conduction Hearing aid still employs bone conduction obtaining an effect equal to hearing by means of using the ears. It amplifies sound but instead of it passing into the ear canal, the sound is carried through the bone in the skull. This is where the name bone conduction originated. It consists of a typical hearing aid but more like modified. There is no ear mold and instead of transmitting the sound through the mold, it travels through a wire onto the oscillator placed behind the ear or on the mastoid bone, straight into the cochlea totally bypassing the outer and middle ear. This results into a not as good as hearing through an air conduction hearing aid. The sounds are not perfect. Both the dynamic range and the frequency range are limited somewhat sounding like a telephone. Also, the listener will have difficulty in determining where the sound came from. Nevertheless, they are a great option for people who can't use the conventional hearing aid.

Bone Conduction hearing aids are perfectly suitable for children and people suffering from only a temporary hearing loss. The bone conduction hearing aid somewhat looks like headphones, using a sort of a headband to hold the aid in place. The hearing aid is placed on one side and the oscillator on the other. They are connected by a single wire. For young patients, the headband which is usually metal in material may be customized for a better and comfortable fit. Since the aid is placed behind the ear, the soft skull of a child might suffer from deformity due to the pressure and takes the shape of the hearing aid. The wire connecting the oscillator and the hearing aid is also quite fragile. It is likely to become broken if not handled with care.

The first bone conductions hearing aids were meant to be installed in eyeglasses. The oscillator and the hearing aid is placed on the glasses' stems placed behind the ear. Then, it was not usual to have lenses thinned and with thick lenses, the vibrations are easily felt. This does not turn out to be efficient now when glasses are custom made for fashion and comfort. More commonly, it was not patronized nearly as much as the conventional ones for its design. People may find it a bit embarrassing to wear a metal headband rather than hook a small device like the ear mold types. It is somewhat publicly undesirable. But currently, with the help of advanced technology, it is now possible to implant a bone conduction hearing enhancement device behind the ear so that it becomes almost permanent.

The Bone Anchored Hearing Aid (BAHA) is also a type of hearing aid working through bone conduction. The external part consists of the microphone, the battery and the processor all of which is attached by a screw. Sound vibrations are transmitted from screw to your bone and from the bone to the inner ear or cochlea. However, the BAHA may not be able to produce quality sound compared to the conventional air-conduction hearing aid.

People who benefit more from using the BAHA would be the people who suffer from malformation of the middle, outer or external parts of the ear. Chronic infection of the ear or simple inflammation may prevent patients from using an ordinary air-conduction hearing aid. Some bone diseases may also mean that BAHA, which is of course implanted in the bone, is definitely not an option for patients suffering from it.

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