hearing

or audition

Physiological process of perceiving sound. Hearing entails the transformation of sound vibrations into nerve impulses, which travel to the brain and are interpreted as sounds. Members of two animal groups, arthropods and vertebrates, are capable of sound reception. Hearing enables an animal to sense danger, locate food, find mates, and, in more complex creatures, engage in communication (see animal communication). All vertebrates have two ears, often with an inner chamber housing auditory hair cells (papillae) and an outer eardrum that receives and transmits sound vibrations. Localization of sound depends on the recognition of minute differences in intensity and in the time of arrival of the sound at the two ears. Sound reception in mammals is generally well developed and often highly specialized, as in bats and dolphins, which use echolocation, and whales and elephants, which can hear mating calls from tens or even hundreds of miles away. Dogs and other canines can similarly detect faraway sounds. The human ear can detect frequencies of 20–20,000 hertz (Hz); it is most sensitive to those between 1,000 and 3,000 Hz. Impulses travel along the central auditory pathway from the cochlear nerve to the medulla to the cerebral cortex. Hearing may be impaired by disease, injury, or old age; some disorders, including deafness, may be congenital. See also hearing aid.

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