Humanities › History & Culture Inventions and Innovations for the Hearing Impaired Share Flipboard Email Print A family conversing in sign language. Getty Images / Huntstock History & Culture Inventions Famous Inventions Famous Inventors Patents & Trademarks Invention Timelines Computers & The Internet American History African American History African History Ancient History and Culture Asian History European History Genealogy Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By Mary Bellis Inventions Expert Mary Bellis covered inventions and inventors for ThoughtCo for 18 years. She is known for her independent films and documentaries, including one about Alexander Graham Bell. our editorial process Mary Bellis Updated May 01, 2019 No one person invented sign language; it evolved worldwide in a natural fashion, much the way any language evolved. We can name a few people as the innovators of specific signing manuals. Each language (English, French, German, etc) developed their own respective sign languages at different times. American sign language (ASL) is closely related to French sign language. In 1620, the first book on sign language that contained the manual alphabet was published by Juan Pablo de Bonet.In 1755, Abbe Charles Michel de L’Epee of Paris founded the first free school for deaf people, he used a system of gestures, hand signs, and fingerspelling.In 1778, Samuel Heinicke of Leipzig, Germany founded a public school for deaf people, where he taught speech and speechreading.In 1817, Laurent Clerc and Thomas Hopkins Gallaudet founded America's first school for deaf people, in Hartford, Connecticut.In 1864, Gallaudet College, in Washington, D.C was founded, the only liberal arts college for deaf people in the world. TTY or TDD Telecommunications TDD stands for "Telecommunications Device for the Deaf". It is a method of coupling Tele-Typewriters to telephones. Deaf orthodontist Doctor James C Marsters of Pasadena, California shipped a teletype machine to deaf physicist Robert Weitbrecht in Redwood City, California and requested a way to attach it to the telephone system so that phone communication could take place. The TTY was first developed by Robert Weitbrecht, a deaf physicist. He was also a ham radio operator, familiar with the way hams used teleprinters to communicate over the air. Hearing Aids Hearing aids in their various forms have provided needed amplification of sound for many persons experiencing hearing loss. Since hearing loss is one of the oldest of the known disabilities, attempts to amplify sound go back several centuries. It is unclear who invented the first electric hearing aid, it may have been the Akoulathon, invented in 1898 by Miller Reese Hutchinson and made and sold (1901) by the Akouphone Company of Alabama for $400. A device called the carbon transmitter was needed in both the early telephone and the early electric hearing aid. This transmitter was first commercially available in 1898 and was used to electrically amplify sound. In the 1920s, the carbon transmitter was replaced by the vacuum tube, and later by a transistor. Transistors allowed electric hearing aids to become small and efficient. Cochlear Implants The cochlear implant is a prosthetic replacement for the inner ear or cochlea. The cochlear implant is surgically implanted in the skull behind the ear and electronically stimulates the nerve of hearing with small wires touching the cochlea. External parts of the device include a microphone, a speech processor (for converting sounds into electrical impulses), connecting cables, and a battery. Unlike a hearing aid, which just makes sounds louder, this invention selects information in the speech signal and then produces a pattern of electrical pulses in the patient's ear. It is impossible to make sounds completely natural because a limited amount of electrodes are replacing the function of tens of thousands of hair cells in a normally hearing ear. The implant has evolved over the years and many different teams and individual researchers have contributed to its invention and improvement. In 1957, Djourno and Eyries of France, William House of the House Ear Institute in Los Angeles, Blair Simmons of Stanford University, and Robin Michelson of the University of California, San Francisco, all created and implanted single-channel cochlear devices in human volunteers. In the early 1970s, research teams led by William House of the House Ear Institute in Los Angeles; Graeme Clark of the University of Melbourne, Australia; Blair Simmons and Robert White of Stanford University; Donald Eddington of the University of Utah; and Michael Merzenich of the University of California, San Francisco, begin work on developing multi-electrode cochlear implants with 24 channels. In 1977, Adam Kissiah a NASA engineer with no medical background designed a cochlear implant that is widely used today. In 1991, Blake Wilson greatly improved the implants by sending signals to the electrodes sequentially instead of simultaneously - this increased clarity of sound.