Presbycusis is the loss of hearing that gradually occurs in most individuals as they grow
older. Hearing loss is a common disorder associated with aging.  The loss associated with
presbycusis is usually greater for high-pitched sounds. For example, it may be difficult
for someone to hear the nearby chirping of a bird or the ringing of a telephone. However,
the same person may be able to clearly hear the low-pitched sound of a truck rumbling
down the street.

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There are many causes of presbycusis. Most commonly, it arises from changes in the
inner ear of a person as he or she ages, but presbycusis can also result from complex
changes along the nerve pathways leading to the brain. Presbycusis most often occurs
in both ears, affecting them equally. Because the process of loss is gradual, people who
have presbycusis may not realize that their hearing is diminishing.