The earliest hearing aids were more ornamental than functional. Early 17th literature described “ear trumpets” that were passed down from sailors who used them to communication over the noise of the seas to regular people suffering from hearing loss. Ear trumpets were much like the description, save for the material — usually simple metals or shells. Depending on the fashion, they were made large and small, out of precious metals or just tin. None of them, however, aided hearing very much. At best the sound was amplified only slightly, and even then it was usually the wrong kind of sound: background noise, rather than human speech. The first marked improvements came with the invention of the electric hearing aids.
On this day, April 27, in 1880 Francis D. Clarke and M. G. Foster patented the first electric “device to help the deaf ear” in U.S. The aid worked by amplifying and passing sound through the skull to the inner ear. Clarke and Foster never commercialized their patent, however — that honor went to the “Acousticon”.
The earliest commercial hearing aids in the U.S. did not rely on human bones, but rather a straight microphone on a headband. According the Museum of Hearing Aids (yes, there is such a thing), “This hearing aid consists of a round carbon microphone (with no volume control), and an earphone with a detachable metal headband and an on-off switch on the back.”