A hearing aid is a small electronic device that you wear in or behind your ear. It makes some sounds louder so that a person with hearing loss can listen, communicate, and participate normally in daily activities. A hearing aid can help people hear more in both quiet and noisy situations. However, only one out of five people, who would benefit from a hearing aid, actually use one.
A hearing aid has 4 basic parts: a microphone, computer processing chip, amplifier, and speaker. The hearing aid receives sound through a microphone, which converts the sound waves to electrical signals and sends them to an amplifier. The amplifier increases the power of the signals and then sends them to the ear through a speaker. Not all hearing aids process sound in the same way, each manufacturer has a slightly different algorithm for prescribing gain and compression. This algorithm is fundamental to ensuring maximum speech intelligibility and sound audibility, a hearing aid is much more than just an amplifier.
Hearing aids are primarily useful in improving the hearing, and speech comprehension for people who have hearing loss, as a result of damage to the small sensory cells in the inner ear, called hair cells. A hearing aid magnifies sound vibrations entering the ear. Surviving hair cells detect the larger vibrations, and convert them into neural signals that are passed along to the brain. The greater the damage to a person’s hair cells, the more severe the hearing loss and the greater the hearing aid amplification is needed to make up the difference. However, there are practical limitations to the amount of amplification a hearing aid can provide. In addition, if the inner ear is too damaged, even large vibrations will not be converted into neural signals. In this situation, a hearing aid would be ineffective.
There are three basic styles of hearing aids. The styles differ by size, their placement on or inside the ear, and the degree to which they amplify sound.
Consist of a hard plastic case worn behind the ear and connected to a plastic earmold that fits inside the outer ear. The electronic parts are held in the case behind the ear. Sound travels from the hearing aid through the earmold and into the ear. BTE aids are used by people of all ages for mild to profound hearing loss. Advancements in BTE aid design have lead to the development of open-fit hearing aids. Small, open-fit hearing aids fit behind the ear completely, with only a narrow tube inserted into the ear canal, enabling the canal to remain open. For this reason, open-fit hearing aids may be a good choice for people who experience a buildup of earwax, since this type of aid is less likely to be damaged by such substances. In addition, some people may prefer the open-fit hearing aid because their perception of their voice does not sound ‘plugged up’.
The Hearing Aid fits completely inside the outer ear and is used for mild to severe hearing loss. The case holding the electronic components is made of hard plastic. Some ITE aids may have certain added features installed, such as a Telecoil. A Telecoil is a small magnetic coil that allows users to receive sound through the circuitry of the hearing aid, rather than through its microphone. This makes it easier to hear conversations over the telephone. A Telecoil also helps people hear in public facilities that have installed special sound systems, called induction loop systems. Induction loop systems can be found in many churches, schools, airports, and auditoriums. ITE aids are not usually worn by young children as the casings need to be replaced often as the ear grows.
Fit into the ear canal and are available in two styles. The in-the-canal (ITC) hearing aid is made to fit the size and shape of a person’s ear canal. A completely-in-canal (CIC)hearing aid is nearly hidden in the ear canal. Both types are used for mild to moderately severe hearing loss. Because they are small, canal aids may be difficult for a person to adjust and remove. In addition, canal aids have less space available for batteries and additional devices, such as a Telecoil. They are not usually recommended for young children or for people with severe to profound hearing loss because their reduced size limits their power and volume.