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.
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.