The strategy originally 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. Later in the seventeenth century, smaller versions of these ear trumpets had been adapted to help those with hearing loss; they took the same form, that of a cone-shaped device pointed at the source of the sound and inserted into the ear. 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. Fast-forwarding to the 19th century, the next innovation was a type of acoustic horn sold under the names such as Cornets or Auricles. Although smaller, these devices were still so bulky that they had to be placed on a table or carried in a lady’s purse, using a flexible tube to convey the sound to the ears.
Electric hearing aids came out in 1898 on the heels of the invention of the telephone. They were not too dissimilar from the ear trumpets that preceded them. However they did noticeably expand the range of frequencies that could be amplified. The first hearing aid using vacuum tubes was patented in 1921, but no successful version of it was sold until 1934 because it was so big and bulky. It consisted of a microphone, an ear receiver, an amplifier, and two batteries, which only lasted for a single day. 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. The next round of innovation was fueled by the integrated circuit – first developed in 1958. This technological advancement lasted in 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 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. Digital technology first appeared in commercial hearing aids in 1987. The processor for these hearing aids was quite large and had to be worn on the body while a wire connected the to a receiver in the ear. All-digital hearing aids became available in 1996 and have been the standard ever since. The features and capabilities of modern digital hearing aids are truly marvelous. What will be next in the timeline of hearing aid technology?