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 capture sounds so that you can hear them. Born out of necessity, the earliest tools used to aid hearing came about in the early 17th century. They were the long trumpets that sailors held to their ears to hear the calls of other sailors on distant vessels. These evolved into smaller versions of the ear trumpet in the late 17th century. The ear trumpet was a portable cone or trumpet-shaped device. The narrow end was inserted into the ear and the flared ear was pointed at the sound. Around the same time, the Metal Ear was created and sold to individuals with difficulty hearing. The Metal Ear was molded out of metal in the shape of an oversized ear and worn directly over the actual ear. 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 first electric hearing aids arose out of the invention of the telephone, and appeared in 1898; they basically functioned like ear trumpets, but they did succeed in widening the frequency range people could hear through them. In 1921 the first hearing aid using vacuum tubes was patented, but it wasn’t effectively used until 1934 because of its bulk. To operate, the hearing aid required the vacuum tube, a microphone, an amplifier, a receiver and 2 batteries. When first introduced the batteries only provided for 1 day of use. After that, there were no significant improvements in hearing aids until 1947, when the transistor was invented. It took a full five years – until 1952 – for transistors to find their way into hearing aids. The engineering challenge that had to be solved was keeping the transistors dry since they are very sensitive to moisture. In 1958 the integrated circuit was invented and was quickly incorporated into hearing aids, a trend that continued through the 1970s.
At that point, digital circuitry and microprocessors became available, offering new levels of audio clarity and miniaturization, and they began to be used in hearing aids with features such as noise and feedback management, directional microphones, and multi-band technology. The problem with these improved hearing aids, however, was price and availability; each unit had to be made by hand and often involved a long wait. 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. The first all-digital hearing aid was introduced in 1996, and advances in technology have now made them the standard, possessing features undreamed-of by the 17th-century ladies with their ear trumpets.