A hearing aid is an electronic device which is designed to amplify sound. Electro-Acoustic signifies electrical manipulation of acoustic energy also known as sound. Following are the attributes of hearing aids:

1. Hearing aids amplify sounds to enhance audibility for an individual with hearing impairment thereby helping in communication.

2. Hearing aids assists people all situations whether noisy or quiet.

3. Hearing aids are useful in improving the speech comprehension of a hearing impaired individual which gets affected as a result of damage to the small sensory cells in the inner ear, resulting in sensorineural hearing loss.

4. Hearing aids can be used in all cases such as damage to the hearing as a result of disease, aging, or injury from noise or certain medicines.

A hearing aid magnifies sound vibrations entering the ear wherein the surviving hair cells are able to detect 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 more powerful is the hearing aid required.

Hearing aid consists of four basic parts:

a. Microphone, which picks up sound from the environment and converts it into an electrical signal, which it sends to the amplifier.

b. Amplifier which increases the volume of the sound and sends it to the receiver.

c. Receiver/Speaker changes the electrical signal back into sound and sends it into the ears which then follow the natural pathways.

d. Microchip which governs the functions of the above three and integrates all together.
Powering the hearing aids is a battery which provides 1.2-1.4v of current to run the system.

Hearing aids are broadly classified under two types i.e. – analog hearing aids and digital hearing aids. In an analog hearing aid, sound or acoustic energy is processed and amplified in totality once it is picked up by the microphone. This type of hearing aid works as a loud speaker and increases the volume of all sounds together and most often is undesirable to the user.

A digital hearing aid utilizes digital signal processing wherein the hearing aid picks up sounds from the environment, converts it into a digital format, and then processes the signal using an algorithm before converting it back to sound at the required output level which is then delivered to the ear. Digital hearing aids are flexible and can be used to process sound more selectively than an analog hearing aid.

There are different styles of hearing aids pertaining to different hearing requirements. These include: Body level hearing aid, behind the ear hearing aid, custom made hearing aids which can be further diversified as Completely in the canal (CIC), In the canal (ITC), In the ear (ITE) and the latest advent of Invisible in Canal Hearing aid (IIC Hearing aid).

Posted by Deepti (MASLP)