Hearing Screening Online Training Program

Additional Information and Resources

Types of Hearing Loss


The three main sections of the ear:

  • The outer ear is the part of the ear that starts at the pinna or auricle, extends through the external ear canal, and ends at the eardrum.
  • The middle ear is the part of the ear that begins with the eardrum at the end of the ear canal. It includes three small bones called ossicles that move in response to sound waves entering the ear. This movement helps to conduct the sound into the inner ear. The middle ear also contains the Eustachian (you-stay-shee-un) tube that helps to maintain normal air pressure in the ear.
  • The inner ear contains the sensory organ for hearing called the organ of Corti that is housed in the cochlea (pronounced COKE-lee-uh). The part of the auditory nerve that is located in the inner ear sends impulses from the cochlea to the brain signaling that sound waves have entered the ear. The inner ear also contains the organ of balance called the labyrinth.

Conductive hearing loss:

  • Occurs in the outer ear or middle ear
  • Blocks movement of sound into the ear
  • Typical causes: Wax in ear canal, hole in eardrum, broken ossicle (middle ear bone), middle ear infection
  • Treatment: Usually can be treated medically or surgically; use of amplification devices such as hearing aids to increase the loudness of sounds can help

Sensorineural hearing loss:

  • A problem in the inner ear and/or auditory nerve
  • Causes: Genetics or damage to neurosensory elements. Neurosensory elements are sensory nerves that conduct nerve impulses, in this case hearing impulses, to the brain
  • Treatment: Use of amplification devices like hearing aids or cochlear implants
  • Sensorineural damage affects 17 million Americans [1]
  • About 90 percent of people with hearing impairments have sensorineural hearing loss, making it the most common type of permanent hearing impairment [2]

Mixed hearing loss involves the external or middle ear and the inner ear.

Noise Exposure and Hearing Loss

There are 15,000 to 20,000 tiny hair cells (cilia) in the cochlea in the inner ear that help to transmit sounds to the brain. As an example of what happens when hair cells have been exposed to too much noise, think about when you walk on fresh grass. When you walk on it lightly only a few times it bounces back to its original shape. However, if you walk on the grass often enough or if you trample it, it gets matted down and will not bounce back. Exposure to sounds that are loud enough and/or occur for long enough can damage the ears’ tiny hair cells so that they can no longer bounce back into shape and can no longer transmit sound to the brain. This causes noise-induced hearing loss (NIHL), which is a type of sensorineural hearing loss.

NIHL can be temporary or permanent; it can result instantly from a single loud noise like a firecracker or gunshot, or can occur gradually from repeated exposure to noise. A recent study of American children 6 to 19 years of age found that 12.5 percent (5.2 million) had some level of noise-induced hearing loss [3].

Resources Available for Hearing Loss

"Attention: By selecting many of the links on this page, you will be leaving the Minnesota Department of Health Web site."

American Academy of Pediatrics Otis Media with Effusion
http://pediatrics.aappublications.org/content/113/5/1412.full

Anatomy of the Ear
http://faculty.washington.edu/chudler/gif/aud1.jpg and
http://faculty.washington.edu/chudler/bigear.html

Another Ear Infection?!
http://www.mindspring.com/~drwarren/otitis-m.htm

How Hearing Works
http://deafness.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fwww.hope4hearing.org%2Fanatomy.htm

How We Hear
http://www.hei.org/education/health/howhear.htm

How We Hear presented by the Audiology Awareness Campaign
http://www.audiologyawareness.com/hearinfo_howhear.asp

Review of Anatomy: The Ear & Temporal Bone
http://www.bcm.edu/oto/index.cfm?pmid=15473


References

1. American Speech-Language-Hearing Association (ASHA). Types of hearing loss [Internet]. Rockville (MD): ASHA; c1997-2002 [cited 2003 June 1]. Available at: http://www.asha.org/public/hearing/disorders/types.htm.

2. Center for the Education of the Infant Deaf (CEID). Pediatric resource guide to infant and childhood hearing loss. Berkeley (CA): CEID; 2001.

3. Niskar AS, Kieszak SM, Holmes AE, et al. Estimated prevalence of noise-induced hearing thresholds shifts among children 6 to 19 years of age: The Third National Health and Nutrition Examination Survey, 1988-1994, United States. Pediatrics. 2001; 108:40-3.



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