A
hearing aid is a portable amplifier that helps
individuals with impaired hearing to hear better by amplifying the sounds that are deficient in that individual's hearing. Each hearing aid is custom-fitted to the wearer's hearing loss and physical anatomy, to provide as much clarity of
sound and physical comfort as is possible. Modern hearing
aids are electronic and use tiny batteries.
Development of the Hearing Aid
The hearing aid goes back to the first humans who put their hands behind their ears to hear faint sounds. Until the 20th century the efforts to collect or transport sound more efficiently included reflective surfaces, tubes, and horn-shaped instruments of many sizes and shapes. The development of the modern hearing aid began with Alexander Graham Bell's invention of the telephone in 1876. His invention required a microphone, allowing sound to imprint its waveform on the current supplied by a battery, and an earphone to make the imprinted or analog current drive a diaphragm to reproduce the sound.
The development of small diode and triode vacuum tubes in the 1930s brought electronic amplification to hearing aids. These aids consisted of an earpiece and separate amplifier and
battery packs worn on the body. During the 1940s a single pack unit came into common use and remained the standard for over 20 years. The transistor was gradually incorporated into hearing aids during the late 1950s and early 1960s. Hearing aids rapidly became smaller, and the amplification and battery pack became part of the earpiece, which was worn behind the ear or in the eyeglasses. By the early 1970s the whole hearing aid could
fit within the ear's concha; in the late 1970s an aid that fit in the ear canal was developed.
As miniaturization progressed, fidelity improved, distortion diminished, and discomfort from sudden changes in loudness was reduced. Adjustability, reliability, and battery life increased. During the 1980s and 1990s digital controls for amplifiers and finally totally digital amplifiers were developed. Digital hearing aids now have programmable controls.
Other Kinds of Aids
For individuals with profound hearing losses who cannot be helped by standard hearing aids, cochlear implants may be able to help. The implant can replicate various aspects of the speech spectrum and can improve the understanding of words for both adults and children. Implants cannot restore hearing to normal or even to moderately impaired levels, but they may make the difference between effective communication or silence for some people.
Other assistive devices include separate microphones, transmission through radio, infrared light, or magnetic fields, all of which improve the reception from remote sources. Visual signaling systems to detect telephones or doorbells, vibrating alarm clocks, telephones that transmit typed messages, and captioned television programs provide everyday assistance for people with profound hearing loss.
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