The strategy originally used as a hearing aid remains in use today, the instinctual gesture to cup your hand behind the ear to better capture sounds so that you can hear them. 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. 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. 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. In the 19th century smaller forms of these acoustic horns were marketed as Auricles or 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.
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. 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. 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. 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. 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.