The oldest hearing aid is instinctual, cupping one hand behind the ear and using it to capture faint sounds and thus hear them more clearly. 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.
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. Another type of hearing aid sold in the 17th century was fashioned of metal and worn over the user’s own ears; it was called, unimaginatively enough, the Metal 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. They were usually smaller in size, designed to be carried in a lady’s purse or to be placed on a table with a flexible tube conveying sounds to the user’s 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. It consisted of a microphone, an ear receiver, an amplifier, and two batteries, which only lasted for a single day. Only incremental improvements were made in hearing aids after this until 1947, and the invention of the transistor. 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.
When microprocessors and digital circuitry became available, they too were used in hearing aids, creating features impossible before that time, such as multi-band technology, noise and feedback management, and directional microphones. Unfortunately, these devices were expensive and had to be hand-crafted, requiring a wait of several weeks before you could obtain one. The first commercially successful digital hearing aid was created in 1987, and used a body-worn processor connected via a wire 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.