The technique first used as a hearing aid remains in use to this day, the instinctual desire to cup your hand behind your ear to better collect sounds so that you can hear them. The earliest technological hearing aids were used by sailors in the early 1600s, which took the form of a long trumpet inserted into the ear and used to hear other sailors calling to them over long distances.
Smaller versions of these ear trumpets were used in the later seventeenth century to help people with hearing loss; they were of the same type – a cone or trumpet inserted into the ear and then pointed at the sound. Another form of 17th century hearing aid was called the Metal Ear, and that’s exactly what it was – a pair outsized ears fashioned out of metal and worn over the wearer’s own ears. During the nineteenth century the acoustic horn had been invented and was marketed under names like Auricles and Cornets. These devices were portable, but cumbersome. The end collecting the sounds was generally placed in a strategic orientation on a table or carried in a purse. A flexible tube then carried the sound to the ear.
The invention of the telephone led to the invention in 1898 of the first electric hearing aids; they were primitive and much like the ear trumpets, but they did allow people to hear more frequencies. In 1921 the first hearing aid using vacuum tubes was patented, but it wasn’t effectively used until 1934 because of its bulk. Because of the vacuum tubes, it needed an amplifier, a microphone, an ear receiver, and two batteries that, despite their size, only lasted for a day. Innovation in hearing aids stalled at this point for some time. The next round of development was made possible by the invention of the transistor in 1947. Even then it wasn’t until 1952 that a transistor-based hearing aid became practical, because it turns out that transistors were sensitive to dampness. The invention of the integrated circuit in 1958 led to their first widespread use in hearing aids, a trend that continued until the 1970s.
The digital circuit and the microprocessors allowed hearing aids to take a big leap forward. Many new features became possible such as noise and feedback management and directional microphones. Microprocessors also enabled greater audio clarity and miniaturization. The new technology had its downside too. Since each hearing aid was hand-crafted, prices were very high and wait times were long.
In 1987, however, the first commercially successful digital hearing aid appeared; it was a model with body-worn electronics with a connection to a receiver in the ear. 1996 saw the release of the first all-digital hearing aids, and that technology has been used ever since, constantly improving to provide features that 17th-century users could never have even dreamed of.