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Encyclopedia entry: hearing aid
- Article from:
- The Oxford Companion to the Body
- Author:
Copyright© The Oxford Companion to the Body 2001, originally published by Oxford University Press 2001. (Hide copyright information)
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hearing aid
Artificial instruments to aid hearing have been in use for at least four centuries and may date back even longer. For example, the simple measure of cupping the hand behind the ear is referred to in ancient Roman medical documents. A variety of purely mechanical devices were used from the seventeenth to the nineteenth centuries to increase the size and capacity of the ear to conduct sound. In the twentieth century, these were surpassed by electric hearing aids, which also amplify and, in more recent devices, process sounds in an attempt to improve the perception and recognition of speech and other environmental signals.
Most non-electric aids to
hearing
were portable so as to ...