A hearing aid is a device which aids the hearing by magnifying the sound electrically or mechanically. Mechanical hearing aids like speaking tubes and trumpets have become vintage, but they may be useful for patients having recruitment who cannot tolerate electrical hearing aids. Today most of the hearing aids are electrical hearing aids.

Body level type
This is the common type which is kept in the pocket of the vest, and wire conducts the sound to the earpiece. It is efficient and less costly.

Ear level type

1. Behind the ear type of aid is small. It fits behind the ear which is covered by hair.
2. Spectacle type of hearing aid is hidden in the spectacle frame.
3. Aid is inserted directly into the ear.

The ear level type of aid are costly, bur are less conspicuous.

Indications

• Hearing aids may be used for all types of deafness which cannot be improved by medicines or surgery.
• Patient who refuse surgery may be prescribed hearing aids.

Contra–indication

• Very mild deafness: Usually a hearing aid is not required.
• Unilateral deafness: A person who hears normally with one ear, need not have hearing aid, as the only difficulties he faces are:
1. Inability to hear soft speech spoken on the side of the effected ear.
2. Stereophonic hearing is absent.

Parts

• Microphone collects the sound and converts it into electricity.
• Amplifier magnifies the electrical impulses produced by the microphone, and pass them to the ear–piece.
• Ear–Piece or Receiver is like a speaker which receives the intensified electrical stimulus from the amplifier, and converts it into sound. Some patients prefer bone conduction type of receiver.
• Batteries supply power to the hearing aids.

Features of Hearing Aid

• Off and on switch is provided.
• Volume control: The volume of the amplified sound can be controlled.
• Tone control: The hearing aid not only magnifies the sound, it can also selectively magnify the sound of those frequencies which are not heard well by the effected person. In sensory – neural deafness, the patient usually has a greater hearing loss in the higher frequencies, and a good hearing aid can amplify the sound selectively in higher frequencies.
• Telephonic conversation can be picked up by the induction coil of the hearing aid.

Prescription of a Hearing Aid
The hearing aid should be prescribed after proper examination of the patient, including audiometry. Depending upon the type and severity of deafness, the hearing aid is selected. It should be purchased after giving an adequate trial.

Acceptability
Even though many deaf person do not hear well, they may not like to use the hearing aid for the following reasons:

• Intolerance: Just as some patients cannot tolerate spectacles, these patients do not tolerate the sound magnified by the hearing aid.