Microphone
The microphone is probably the most important part of a hearing aid, for obvious reasons. It is the device that detects and transmits sounds to the speaker. Depending on the type of hearing aid, the microphone can often be located in different positions to increase the hearing aid's functionality. For example, on behind-the-ear hearing aids, the microphone is located on the top of the hearing aid. This design allows the microphone to be located closer to the speaker because the speaker fits inside the person's ear and is shielded from feedback.
Speaker
The speaker is another essential component of a hearing aid. The speaker reproduces the sound collected by the microphone. Most hearing aid speakers are extremely miniaturized. This is possible through the use of neodymium magnet speakers. These magnets are extremely powerful and much smaller than traditional magnets used to drive speakers, which makes them perfect for small hearing aid speakers. These are the same speakers used in earbud headphones. Most hearing aid speakers are located in a housing that is designed to fit snugly in the ear or ear canal.
Internal Components
The transistor revolutionized the hearing aid. It is hard to believe that hearing aids once had external boxes and were powered by cathode ray tubes and required two batteries to power them. The transistor has gotten even smaller since its introduction in the 1950s. In the 1950s the hearing aid was one of the first devices to make use of the transistor. The introduction of the microchip was another advance that allowed the hearing aid to be further miniaturized. Microchips allow several transistors to be packed into one small chip. This advance has allowed hearing aids to become smaller and smaller, to the point where some hearing aids can be placed inside the ear. Without the transistor it would not be possible for the hearing aid to be as small as it is today.
