A hearing aid (Hearing Aid) is a small amplification device for deaf people to compensate for hearing loss. Its development history can be divided into the following seven eras: the era of palm collection, the era of carbon, vacuum tubes, transistors, integrated circuits, The era of microprocessors and digital hearing aids.
The earliest and most practical “hearing aid” of mankind may be the deaf person’s own palm. 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 the most natural hearing aid method. Up to 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 successively invented simple mechanical devices of various shapes, such as “ear horns” like horns or screw horns, wooden “listening boards”, “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, etc. 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 someone speaking, he held the ear tube in his hand and stretched it to someone else’s mouth. It looks funny, but it improves the hearing of the deaf. At the same time, remind the speaker 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.
When Was The First Hearing Aid Invented?
The earphone was invented in the 17th century and is considered the first device used to help the hearing impaired. These trumpets come in many shapes and sizes, from iron skin to animal horns. It was not until the end of the 18th century that the invention of the foldable ear horn saw the next advancement. Frederick C. Rein took the lead in commercializing these speakers in 1800. To make this device less noticeable, Rein created an acoustic headband that hides the sound device in the user’s hair. How about the first hearing aid? In 1878, American scientist Bell invented the first charcoal hearing aid This kind of hearing aid is assembled from carbon microphones, earphones, batteries, wires, and other components. In 1890, Austrian scientist Ferdinant Alt produced the first generation of electronic tube hearing aids. In 1904, Danish Hans Demand 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, bulky like a 17-inch TV, and not easy to carry, etc.
The First Portable Hearing Aid.
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, realizing the separation of the main unit and the battery. In 1921, Britain produced the first commercial electronic tube hearing aid. Since 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 the battery and hearing aid can finally 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 the 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 the mass production of hearing aids, one is Oticon and the other is Danavox. Hearing aids are getting smaller and smaller. Finally, they are as big as a cigarette box and are 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 BTE hearing aid was made, which not only further reduced the volume, but also surpassed the glasses-type and box-type hearing aids, and became the world’s most sold 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 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, China began to produce box-type hearing aids, and now it can produce in-ear and behind-the-ear hearing aids.
The programmable hearing aid that appeared in 1988 uses the remote control to change multiple listening programs to achieve the most 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. The common feature of all hearing aids of digital technology is the analog technology used for sound processing. The development of digital sound processing technology has greatly improved the efficiency of hearing aids. The digital hearing aid consists of a small programmable computer that can very accurately amplify millions of different sound signals, thereby improving the hearing of the hearing impaired.
In the mid-1980s, the first digital hearing aids came out, but these early models were not practical. It was not until the late 1990s that digital hearing aids were truly successful when people placed small digital devices in or behind their ears. Within a few years, digital technology replaced the old analog technology, and all hearing aids became digital. Nowadays, almost all modern digital hearing aids are advanced smart devices that can automatically adapt to the environment and listening situation, thereby providing the best list experience under actual conditions. They can also use Bluetooth technology or other connection technologies to connect to other electronic devices, such as smartphones and TVs. Digital hearing aids can improve the hearing of people with weak hearing so that even people with severe hearing loss can lead almost normal lives. Digital hearing aids have a decisive impact on the quality of life and health of many people with hearing loss.