Early bone conduction hearing aid devices.

The concept of bone conduction hearing is old. By the 16th century the conduction of sound by a rod or the staff of a spear was reported by a number of writers; however, these writers considered these phenomena as a curiosity rather than having practical value. In the 17th century, John Bulwer and George Sibscota, both interested in the deaf and their education, applied the bone conduction phenomenon as an aid to defective hearing. Soon, independent reports from Germany, France, and Italy also described bone conduction rod devices as aids to impaired hearing. In 1879, the Audiphone, a hearing fan that operated by bone conduction, was patented. The invention of the Audiphone triggered the development and sale of a number of similar devices that had considerable popularity until the invention of the carbon-electric hearing aid in the early 1900s.