Structure of hearing aids

Since the beginning of the 20th century, when electronic hearing aids were introduced, the structure of hearing aids has not changed much, and is still composed of microphones, amplifiers, receivers, and power supplies. However, the size of each part of the hearing aid has gradually decreased, the sound quality has gradually improved, and there are more selective controls.
1 Microphone: collects sound and converts it into radio waves.
2 Amplifier: increases the intensity of radio waves.
3 Receiver: just the opposite of the microphone, converting the increased electrical energy back into sound waves.
4 Power supply: small battery.
5 Shell: protects the internal structure.