When Was The Hearing Aid Invented And What Is The History Of The Development Of Hearing Aids?

The hearing aid (Hearing Aid) is a small amplification device for the deaf to compensate for hearing loss. Its development history can be divided into the following seven eras: the palm collection era, the carbon era, the vacuum tube, the transistor, the integrated circuit, The era of microprocessors, and digital hearing aids.

The earliest and most practical "hearing aid" of mankind may be the palm of the deaf person's own hand. Place the palm of your hand near your ear to form a semi-circular horn shape, which can collect sound well. Although the gain effect of this method is only about 3dB, and it is not a hearing aid in the modern sense, it is a natural hearing aid method. Until now, we can still see some elderly people using their palms to collect sounds while listening to others. Many mammals have huge ears, so their hearing is much better than humans.

Inspired by the sound collection of the palms, some interested people have invented simple mechanical devices of various shapes, such as "ear horns" like horns or screw horns, wooden "soundboards", "sound tubes", and hats. The "listening cap" and "listening bottle" like a bottle, the "ear fan wings" like a fan and animal wings, and a very long "speaking tube" like a stethoscope, and so on. Because people think that the longer the listening tube, the better the sound collection effect, so some listening tubes are as long as tens of centimeters, or even more than one meter. When listening to other people's speech, hold the ear tube and stretch it to others' mouths. It looks funny and ridiculous, but it improves the hearing of deaf people. At the same time, the speaker is also reminded to speak as loudly as possible. This simple mechanical hearing aid has been used for hundreds of years. It was not until the nineteenth century that it was gradually replaced by charcoal telephone hearing aids.

In 1878, American scientist Bell invented the Taiwan charcoal hearing aid. This kind of hearing aid is assembled from carbon microphones, earphones, batteries, wires, and other components.

In 1890, the Austrian scientist Ferdinant Alt produced a new tube hearing aid.

In 1904, Danish Hans Demant and American Resse Hutchison jointly invested in the mass production of hearing aids. By the 1940s, there were already two types of hearing aids, air conduction, and bone conduction. Hearing aids in this period have been greatly developed and improved in technology. Although they can meet the needs of some deaf people, they still have many shortcomings, such as too much noise, being bulky like a 17-inch TV, and not being easy to carry, etc.

In 1920, shortly after the thermionic vacuum tube (hot cathode electron tube) came out, vacuum tube hearing aids appeared. With the continuous development of vacuum tube technology, the volume of hearing aids has gradually become smaller, and the separation of the main unit and the battery has been realized.

In 1921, Britain produced a commercial electronic tube hearing aid. Because the tube needs two power supplies (one is to heat the filament in the tube to release electrons; the other is to drive the electrons to reach the anode through the electric grid), so this kind of hearing aid is bulky and heavy, although the gain and clarity are better, It is almost impossible to carry. With the passage of time, mercury batteries have replaced zinc batteries, significantly reducing the size of the battery, and finally, the battery and hearing aid can be integrated. During the Second World War, new technical materials such as printed circuits and ceramic capacitors appeared, which significantly reduced the volume of integrated hearing aids, so that hearing aids could be carried around. Gradually, hearing aids have also adopted techniques such as peak clipping (PC) and compression (automatic gain control, AGC).

In 1943, the development of integrated hearing aids began. The power supply, microphone, and amplifier were put in a small box, which was the prototype of modern box-type hearing aids. In the same year, Denmark established two factories for mass production of hearing aids, one is Oticon and the other is Danavox. The volume of hearing aids is also getting smaller and smaller. In the future, they will be as big as a cigarette box, making them very convenient to carry.

In 1948, when semiconductors came out, electronic engineers immediately applied semiconductor technology to hearing aids and achieved better results. The use of a part of semiconductor components can further reduce the volume of the hearing aid. If all semiconductor components are used, acoustic feedback will be inevitable.

In 1953, transistor hearing aids came out, which provided the possibility of miniaturization of hearing aids.

In 1954, glasses-type hearing aids appeared. In order to avoid acoustic feedback, the designer installed the receiver and microphone on the two temples but failed to achieve binaural wear. In 1955, a spectacle-type hearing aid with the entire body on a single temple was introduced, making it possible to wear hearing aids in both ears at the same time.

In 1956, the behind-the-ear hearing aid was made, which not only further reduced its volume, but also surpassed spectacle-type and box-type hearing aids, and became the world's largest-selling hearing aid.

In 1957, in-ear hearing aids came out. The new ceramic microphone has a wide and flat frequency response, which overcomes the shortcomings of the previous piezoelectric crystals. The appearance of tantalum capacitors has further reduced the volume of capacitors, and transistor circuits have developed rapidly in the direction of miniaturization of integrated circuits.

With the advent of large-scale integrated circuits, the volume of hearing aids has been further reduced. Soon after the emergence of in-ear hearing aids, semi-concha-cavity, ear canal, and complete ear canal hearing aids have appeared one after another, which satisfies patients to a large extent. Psychological and aesthetic needs.

In 1958, my country began to produce box-type hearing aids, and now it has been able to produce in-ear and behind-the-ear hearing aids.

The programmable hearing aid that appeared in 1988 uses a remote control to change multiple listening programs to achieve a comfortable listening experience. Programmable hearing aids use wide-angle microphones and directional microphone hearing aids, which can use different listening modes in daily life and in noisy environments to make the sound heard more clearly. Although the person wearing a directional hearing aid is not looking at you, he is listening intently to your speech, so it seems that there is a special purpose for monitoring. It is rumored that former US President Clinton wore such hearing aids.

In recent years, "digital" hearing aids have been introduced, which have extremely strong digital signal processing capabilities and provide greater flexibility for selection.

After more than a hundred years of ups and downs, today's hearing aids have had various shapes such as in-ear, back-of-the-ear, box, glasses, hairpin, pen, and wireless, and the hearing aid effect has been significantly improved. We believe that in the near future, the size of hearing aids will become smaller and smaller, their functions will become more and more powerful, and they will benefit all deaf people.