deafness
Partial or total deficit of hearing in either ear. Of assistance are hearing aids, lip-reading, a cochlear implant in the ear in combination with a special electronic processor, sign language, and ‘cued speech’ (manual clarification of ambiguous lip movement during speech). Approximately 10% of people worldwide experience some hearing difficulties. This amounts to approximately 28 million people in the USA alone.
Conductive deafness is due to faulty conduction of sound inwards from the external ear, usually due to infection (see otitis), or a hereditary abnormality of the bones of the inner ear (see otosclerosis).
Perceptive deafness may be inborn or caused by injury or disease of the cochlea, auditory nerve, or the hearing centres in the brain. It becomes more common with age.
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