This was a study of the history of the technological development of air conduction hearing aids, and a review of international literature on the subject. The technological evolution of amplification devices, from their origin to the present day, can be divided into seven distinct periods: the period of sound collectors, the period of hearing devices constructed from carbon, the period of vacuum tubes, the transistor period, the period of integrated circuits, the microprocessor period and the period of digital hearing instruments. Throughout these different stages, hearing instruments have progressively developed reaching their present state.

The current era is itself undergoing constant development and change. With the introduction of new technologies, we expect that the rate of change will increase rapidly in the future.