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Device that increases the loudness of sounds in the user's ear. Its principal components are a microphone, an amplifier, and an earphone. Hearing aids are increasingly smaller and less conspicuous, fitting behind the earlobe or within the ear canal. They have widely differing characteristics, amplifying different components of speech sounds for maximum comprehension by each wearer. Hearing aids with automatic volume control vary the amplification automatically with the input.
This entry comes from Encyclopædia Britannica Concise. For the full entry on hearing aid, visit Britannica.com.