What is a hearing aid?
A hearing aid is a device which amplifies the sound and thus improves the hearing.
How are hearing aids classified?
Hearing aids can be classified into:
- Air conduction hearing aids
- Bone conduction hearing aids
- Environmental aids
About Air conduction hearing aids:
They are most commonly prescribed. Here the amplified sound is transmitted via the external auditory canal to the tympanic membrane.
Types of Air conduction hearing aids
- Body worn type:
The microphone and amplifier with the battery are worn on the chest while receiver is at the ear. Used in severely deaf persons and congenital deafness.
- Behind the ear:
The whole hearing aid unit is worn behind the ear. Sound is transmitted to ear canal via a silicon tube or mould. This type is useful in moderate to severe hearing loss and cosmetically better. It is also easier to maintain.
- In the Ear:
The whole hearing aid is in a mould fitted in the ear canal. It is useful in mild to moderate loss. Cosmetically, it is very good.
- In the canal:
This one is also called invisible hearing aid. The whole unit is in the external canal. It is useful in mild to moderate hearing loss. This has excellent cosmetic results.
- Spectacle type:
The unit is incorporated in the auricular part of spectacle frame Not very popular.
- Programmable heavy aids / Computerized hearing aids:
These aids can be programmed according to needs of the patients and environmental conditions. They can be used in any degree of hearing loss.
What are the mechanics of a hearing aid?
Hearing aid has 5 main parts:
- Microphone: It fits into the hearing aid, collects sound energy and converts it into electrical energy.
- Amplifier: Increases the amplitude of impulses generated.
- Earphone: Converts electrical energy into sound.
- Battery: Provides power supply.
- Mould: Holds the hearing aid in place and acts like a seal.
What are the indications for hearing aids?
- Hearing loss due to damage or weakness of the Hearing nerve(Sensorineural hearing loss) due to various reasons like presbyacusis, ototoxicity.
- Patients with conductive hearing loss like otosclerosis, chronic suppurative otitis media (safe type) who are unfit or unwilling for surgery.
Some popular hearing aids: