Hearing aid

In 1880, the first U.S. patent for an electric hearing aid was issued to Francis D. Clarke and M.G. Foster, titled a Device for Aiding the Deaf to Hear (No. 226,902). The device employed bone conduction by which sound is passed through vibration of the skull bone. It was not until 1901 that the first commercially available hearing aid was produced, the Acousticon, invented by Miller Reese Hutchinson..