Hearing Losses
Hearing loss and deafness can affect individuals of all ages. Approximately 1% of the babies born, have a hearing loss. A hearing loss or deafness has no bearing on a person's intellectual capacity or ability to learn. However, information, that the hearing child absorbs automatically through listening, often requires direct teaching for the child with a hearing loss. The services of a teacher of the deaf are beneficial in order to maximize learning potential. The impact on language development, communication, and learning in general can be severe, and a concentration of individual academic support is needed to make an even playing field. It is also useful to remember that sometimes a loss can occur only in the high or low frequencies. This loss will compromise the ability to hear specific speech sounds which may be absent or distorted or confused with other speech sounds which can have direct impact on spelling. Hearing can fluctuate depending on the student's state of health, background noise or room acoustics. A hearing loss can occur in both ears (bilateral) or in one ear (unilateral) and rarely will the loss be the same in both ears.
The outer part of the ear, the pinna and the ear canal, collects the sound and directs it through the auditory canal to the eardrum. The pinna is specifically designed to match the particular needs of a species. The elephant's large ears are designed to hear low sounds like the thundering of other elephants. The mouse's ears are small and hear very high sounds relevant to their catching their food. As the sound waves hit the eardrum, it vibrates causing 3 little bones, the ossicles, in the middle ear to move. Essentially, the middle ear is just space filled with air except for these 3 tiny bones, the hammer (malleus), anvil (incus) and stirrup (stapes) which can all fit on the surface of a penny. The oval window is the entry point to the inner ear. On the one side of the oval window the stirrup is attached; on the other side, the cochlea. The cochea, the size of the tip of th little finger, looks like a snail's shell. It is filled with fluid and lined with more than 20,0000 tiny hair cells that moves back and forth in response to the sound, like seaweed in water. They interpret the different pitches of sound, the higher sounds closer to the oval window; the lower ones further away, and then pass the information in the form of electrical impulses to the auditory nerve which carries the information to the brain to interpret back into sound. If these hair cells are damaged, the resulting hearing loss cannot be repaired. It is usually the outer hair cells which carry the high frequency and amplification of sounds which are damaged first. The inner ear is also the home of the semi-circular canals which monitors our balance.
Coquitlam, B.C. School District #43
Conductive Hearing Loss: is located in the outer or middle ear. Middle ear infections (otitus media), perforated ear drums, blocked auditory canals can cause a mild to moderate loss which generally present as being uniform across the frequencies and results in sound being softer or sounding muffled. This hearing loss responds to medication and/or surgery.
Sensorineural Hearing Loss: is located in the inner ear either in the cochlea as a result of damage to the delicate sensory hair cells, or in auditory nerve which transmits sound to the brain. This loss is a permanent and doesn’t respond to medical intervention. This loss can vary from mild to profound and often allows a person to hear certain frequencies but not others. Even with amplification, sound may be distorted so that the use of hearing aids may not be a viable option. A cochlear implant may be an option.
Mixed Hearing Loss: is a combination of both a conductive and sensorineural loss so that there is inner ear as well as outer or middle ear involvement.
www.kidshealth.org/kid/body/ear_noSW.html
http://library.thinkquest.org/15390/causes.htm