The earliest hearing aid is instinctual, cupping one hand behind the ear and using it to capture noises and thus hear them more clearly. The first real hearing aids, however, were the long trumpets used by sailors to hear the voices of other sailors calling to them over long distances at sea. 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. 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. 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. A hearing aid using vacuum tubes was patented in 1921. The vacuum tube – based hearing aids wasn’t commercialized and sold to the public until 1934 because of its large size and 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. 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. Unfortunately, transistors were also sensitive to dampness, so it took until 1952 until usable transistor-based hearing aids were made available. 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 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. 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.