Hearing aid (kaan ki machine)- A hearing aid is an electronic device that placed inside the ear.it includes a microphone and a processor that pick up sound and process it.An amplifier then converts the sound into an electrical signal.The power of the amplifier depends on the type of hearing loss and the level of the surrounding sounds.These devices are typically rechargeable or disposable, and may have various other special features.Read on for more information on the different types of hearing aid.