I can't hear you: The invention of the Hearing Aid

Hearing aids are devices that amplify sound so a person who has a hearing impairment can enjoy sounds from a musical symphony to a lively conversation to the rustle of leaves. Two types of hearing aids either conduct sound through the air or through bone. Usually a person who is hearing impaired can use an air-conductionhearing aid, as it amplifies sound and brings it directly to the ear. The bone-conduction hearing aid brings sound waves to the bony part of the head behind the ear and uses the bone to transmit sound waves to the nerves of the ear. A typical hearing aid contains a microphone that picks up sounds and converts them into electric signals, an amplifier, which increases the strength of the electric signals, and the receiver, which converts the signals back into sound waves that can be heard by the wearer. There are three main styles of hearing aids: those that fit behind the ear, those that fit into the ear, and those which slip into the ear canal. Power is provided by a small battery.

Devices to aid hearing have a long history. An artificial ear drum was devised in 1852 when an English physician, Joseph Toynbee, used a disk of vulcanized rubber attached to a rod. The Victorian era was known for some of its more elaborate concealed hearing devices, in urns, top-hats, even tiaras.

In the 1870s, Alexander Graham Bell began experimenting with the conduction of sound through electrical devices originally intending to help deaf children hear. His experiments led to the invention of the telephone instead, but his work did bring public awareness to the needs of the hearing impaired.

The first electrical hearing aid was made in 1901 by Miller Reese Hutchinson and he called it the Telephone-Transmitter. During the era of vacuum tubes, like those used in early radio, new hearing aids were developed starting in 1920 with Earl Charles Hanson's Vactuphone. A 1923 model produced by the Marconi Company was the Otophone, consisting of an amplifier placed in a large case weighing 16 pounds (7 kg) making it rather bulky to use.

The first "wearable" hearing aid weighed 2.5 pounds (1.1 kg) and was made by A. Edwin Steven in 1935. During the 1950s transistors revolutionized electronics and Microtone introduced its compact and powerful transistor hearing aid in 1953.

For individuals whose hearing cannot be aided with a hearing aid, there is the possibility of having a cochlear implant, the first of which were done in 1973 and which involved the implantation of an electrical device which stimulated the remaining nerves in the inner ear in people suffering from nerve deafness.

Although the implant did not restore normal hearing, it helped the recipient hear and interpret environmental sound. Today, multichannel electrical cochlear implants are more sophisticated and contain speech processors which allow some patients to understand speech without reading lips.

Digital hearing aids in which a computer- controlled sound processor is contained, are also available.