Hearing loss is the gradual or sudden inability to fully perceive sound. About 28 million Americans have some level of hearing impairment, according to the National Institute on Deafness and Other Communication Disorders (NIDCD).

A person perceives sound when structures inside the ear convert sound wave vibrations into nerve signals, which are then perceived by the brain as individual sounds. Hearing loss can be temporary or permanent. Permanent hearing loss usually results from damage to the inner ear structure (called the cochlea) responsible for processing these nerve signals.

There are three major types of hearing loss:

• Conductive hearing loss. Occurs when the external or middle ear fails to work properly. This form of hearing loss generally can be reversed by treating the underlying condition that may be responsible.
  
  
• Sensorineural hearing loss. Usually occurs due to disorders of the cochlea in the inner ear. Aging is the most common cause of this type of hearing loss. This type of hearing loss generally is not reversible.
  
  
• Mixed hearing loss. Occurs as a result of both conductive and sensorineural factors

People who experience hearing loss may perceive a muffled quality to speech and other sounds. They often have difficulty in understanding other people's words. This problem tends to worsen in situations where there is a lot of background noise, such as in a room full of people. Various symptoms may be related to hearing loss. Ringing in the ears (tinnitus) is one of these symptoms.

Treatment options depend on the cause of a patient’s hearing loss. Patients whose hearing loss is related to earwax blockage usually can fully restore their hearing simply by having the earwax removed by a physician. Permanent hearing loss may be treated using artificial devices such as hearing aids, cochlear implants or personal listening devices.

Hearing loss is usually a natural and inevitable result of the aging process. Nonetheless, people can reduce the risk of hearing loss by using proper hearing protection in noisy environments and avoiding excessive noise whenever possible.