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Causes
By Mayo Clinic staff
Some causes of hearing loss include damage to the inner ear, a buildup of earwax, infections and a ruptured eardrum. To understand how hearing loss occurs, it can be helpful to understand how you hear.
How you hear
Hearing occurs when sound waves reach the structures inside your ear, where the sound wave vibrations are converted into nerve signals that your brain recognizes as sound.
Your ear consists of three major areas: outer ear, middle ear and inner ear. Sound waves pass through the outer ear and cause vibrations at the eardrum. The eardrum and three small bones of the middle ear — the hammer, anvil and stirrup — amplify the vibrations as they travel to the inner ear. There, the vibrations pass through fluid in the cochlea, a snail-shaped structure in the inner ear.
Attached to nerve cells in the cochlea are thousands of tiny hairs that help translate sound vibrations into electrical signals that are transmitted to your brain. The vibrations of different sounds affect these tiny hairs in different ways, causing the nerve cells to send different signals to your brain. That's how you distinguish one sound from another.
How hearing loss can occur
Causes of hearing loss include:
- Damage to the inner ear. Aging and prolonged exposure to loud noise may cause wear and tear on the hairs or nerve cells in the cochlea that send sound signals to the brain. When these hairs or nerve cells are damaged or missing, electrical signals aren't transmitted as efficiently, and hearing loss occurs. Higher pitched tones may become muffled to you. It may become difficult for you to pick out words against background noise. Heredity may make you more prone to these changes. This type of hearing loss is known as sensorineural hearing loss, which is permanent.
- A gradual buildup of earwax. Earwax can block the ear canal and prevent conduction of sound waves. Earwax blockage is a cause of hearing loss among people of all ages. This causes conductive hearing loss, which usually can be restored with earwax removal.
- Ear infection and abnormal bone growths or tumors. In the outer or middle ear, any of these can cause hearing loss.
- Ruptured eardrum (tympanic membrane perforation). Loud blasts of noise, sudden changes in pressure, poking your eardrum with an object and infection can cause your eardrum to rupture and affect your hearing.
- Hearing loss. National Institute on Deafness and Other Communication Disorders. http://nihseniorhealth.gov/hearingloss/hearinglossdefined/01.html. Accessed April 21, 2011.
- Weber PC. Evaluation of hearing loss in adults. http://www.uptodate.com/home/index.html. Accessed April 21, 2011.
- Lustig LR, et al. Ear, nose, & throat disorders. In: McPhee SJ, et al. Current Medical Diagnosis and Treatment 2011. 50th ed. New York, N.Y.: The McGraw-Hill Companies; 2011. http://www.accessmedicine.com/content.aspx?aID=2613. Accessed April 25, 2011.
- Weber PC. Etiology of hearing loss in adults. http://www.uptodate.com/home/index.html. Accessed April 21, 2011.
- Weener DJ, et al. Evaluation and management of hearing loss in older adults. Clinical Geriatrics. 2010;18:20.
- Common sounds. National Institute on Deafness and Other Communication Disorders. http://www.nidcd.nih.gov/health/education/teachers/common_sounds.asp. Accessed April 21, 2011.
- Learn more about hearing loss prevention: Noise meter. National Institute for Occupational Safety and Health. http://198.246.98.21/niosh/topics/noise/abouthlp/noisemeter_flash/soundMeter_flash.html. Accessed April 28, 2011.
- Occupational noise exposure — 1910.95. U.S. Department of Labor. http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=STANDARDS&p_id=9735. Accessed April 28, 2011.
- How loud is too loud? American Tinnitus Association. http://www.ata.org/about-tinnitus/how-loud-too-loud. Accessed April 28, 2011.
- Isaacson B. Hearing Loss. The Medical Clinics of North America. 2010;94:973.
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