This article tells the story of how research into the structure of the inner ear was combined with research in the telecommunications industry to produce a device which enables deaf people to hear.

The ancient Greeks had some understanding of sound transmission in the human ear. However, it was not until the sixteenth century that details began to be filled in, a process which is still ongoing (see Early Beginnings). As scientists began to research the structure of the ear, they also attempted to understand how sound is received and interpreted by the ear and the brain. They realized that the hair cells inside the cochlea in the ear played an important role in the whole process of hearing different tones (see How the Inner Ear Recognizes Sound). Meanwhile, physicians were studying deafness and characterizing the various types of hearing loss (see When Hearing is Lost). Beginning in the late 1950s, researchers began to wonder if they could replace the signals from the hair cells that were so important to hearing. Their efforts to create a cochlear implant met with substantial success. By the early 1970s, several groups were working on developing more sophisticated hearing devices. Physicians collaborated with engineers who were working on sending signals along telephone lines (see Cochlear Implant Technology Develops).

In the meantime, scientists were also studying how sound information is encoded in the auditory nerve and the brain. Their research on nerves and stimuli has not yet been fully incorporated into the development of modern hearing aids (see What Does the Cochlea Tell the Brain?). Currently, the function of hair cells can be replaced using cochlear implants, but researchers hope to be able to repair the hair cells someday. Researchers have made significant progress in understanding how these hair cells transmit signals to the brain (see How Hair Cells Work). One of the stranger discoveries made about hearing in recent years has been finding that the cochlea not only receives sounds, but can also produce sounds such as ringing in the ears. Researchers are currently working on determining what causes these “otoacoustic” emissions, as well as studying how hair cells are damaged and how they might be repaired (see The Inner Ear Produces Sound).

This article is available in Spanish and Japanese.