Hearing aids have had a long history. In 1588, Giovanni Battista Porta was the first to mention hearing aids in his book Natural Magick, in which he describes wooden hearing aids carved to look like ears belonging to animals with superior hearing.
During the 17th and 18th century, hearing aid “trumpets” that were funnel- or tubular-shaped, wide at one end and narrow at the other, which collected sound waves and funneled them towards the ear. These hearing aids, often made from animal horn in the early days and copper or brass later on, were acoustic and offered only moderate amplification. While somewhat effective, older hearing aids were cumbersome and unattractive. In the 1800s, hearing aids makers began creating devices users could disguise as decorative accessories.
Alexander Graham Bell’s telephone, patented in 1876, was the first electrical device capable of transmitting speech. Many hearing-impaired people found it easier to understand speech through Bell’s telephone receiver than to listen to someone in person.
Thomas Edison did not find the telephone helpful in overcoming his hearing problem and this inspired him to improve the receiver. In 1878, Edison introduced the carbon transmitter that amplified the electrical signal. Other inventors followed in step, trying to adapt telephone technologies as hearing aids but most were heavy and obtrusive. These cumbersome devices did not work very well, amplifying speech by a maximum of 15 decibels, which is weak in comparison to the 60 dB volume of a normal conversation.
Bone conduction emerged as an effective hearing aid in the 17th century. In this approach, the bones of the skull conduct sound to the inner ear. The Audiphone, a hearing fan operated by bone conduction, received a patent in 1879. Other manufacturers followed suit and developed similar devices, which gained considerable popularity until the early 1900s when the development of electrical technologies created new possibilities for sound amplification.
The Modern Hearing Aid
The vacuum tube revolutionized hearing aid technology. In their hearing aids introduced in 1920, Western Electric Co. used the three-element tube invented by Lee De Forest. These technically superior hearing aids provided 70 dB of amplification. Unfortunately, they were as big as filing cabinets and weighed more than 220 pounds. Western Electric Co. introduced another model in 1924. The components fit into a small wooden box that weighed just over 8 pounds but it was still conspicuous.
Aurex Corp. created the first wearable hearing aid in 1938 but the early versions required a separate, strap-on battery. World War II brought two major innovations to hearing aid technology – printed circuit boards and button batteries – that allowed for smaller, more reliable models. Batteries, microphone, and amplifier fit into a single housing that fit into the user’s shirt pocket.
The invention of the transistor in 1948 allowed manufacturers to create still smaller hearing aids. In the late 1950s, the Otarion Listener became the first hearing aid worn entirely at the ear; the electronics were held in the temple piece of a pair of eyeglasses. Zenith Radio came out with the first behind-the-ear model in 1964.
By the 1980s, manufacturers were introducing digital technology into hearing aids to create hybrid analog-digital models. The first fully digital models debuted in 1996 and programmable models emerged in 2000. Today, digital technology helps the modern hearing aid excel at amplification and controlling feedback.