1. What causes hearing loss?
Problems in the outer, middle, and inner ear

2. The Outer Ear
Anything that completely blocks the ear canal can cause hearing loss.
Blockage with earwax (also called cerumen) is common.
Infections with swelling that shuts the ear canal
Foreign bodies in the ear
An injury
Birth defects
A growth in the ear canal

3. Normal view of ear drum Blocked by growths in the ear canal

4. How would an ear canal blockage cause hearing loss?
Any of these, including blockage by wax, may result in conductive hearing loss .
That is, it interferes with sound conduction and is generally correctable.
It causes decrease in volume but does not generally produce distortion.

5. The Middle Ear
Problems that can affect the middle ear and lead to hearing loss include:
Ear infections
Fluid in the ear
Otosclerosis
Birth defects
Tumors

6. Ear Infections & Fluid in the Ear
Middle ear infections cause swelling of the lining in the middle ear, and often an accumulation of fluid.

7. Fluid build-up is caused by a malfunction of the Eustachian tube, which connects the ear with the back of the throat.
The job of the Eustachian tube is to equalize the pressure in the middle ear. (It makes your ears “pop”)

8. How would this cause hearing loss?
Normal ear drum
How would this cause hearing loss?
Fluid behind the ear drum

9. It sometimes requires drainage through a myringotomy or with the placement of ear tubes .

10. Otosclerosis
A hereditary disease in which new bone is deposited around one of the tiny bones in the middle ear, specifically around the footplate of the stapes (or 'stirrup') bone.
How would this cause hearing loss?

11. The Inner Ear
There are many conditions that cause the delicate inner portion of the ear to function abnormally.
They include:
Otosclerosis
Presbycusis
Fistula
Head injury
Meniere's syndrome
Noise
Infections
Sudden deafness
Neural problems

12. Presbycusis
The natural aging process also causes sensorineural hearing loss.
the damage lies in the inner ear, the auditory nerve, or both.
Beginning shortly after birth, we begin to lose hair cells and nerve endings within the cochlea.
How would this cause hearing loss?

13. Noise Noise is an important cause of hearing loss.
An estimated 7 to 10 million people in American industry have noise-induced hearing loss, virtually all of which was preventable.
In addition to industrial noise, recreational noise can damage hearing.
Such noise is encountered commonly from power tools, motorcycles, loud music (especially with earphones), etc.

14. How would this cause hearing loss?
Neural problems
Neural (nerve-related) problems may also produce hearing loss. Among the more common are:
Acoustic neuroma , a common tumor of the acoustic nerve
Multiple sclerosis
Autoimmune sensorineural hearing loss, in which the body attacks its own ear
Ototoxicity, which is hearing loss caused by a substance that gets into the body
most often the substance is a medication (antibiotic, etc.).
How would this cause hearing loss?

15. Hearing Aids and Cochlear Implants

16. Hearing aids are fairly simple devices, consisting of four basic parts:
A microphone picks up sound from the environment and converts it into an electrical signal, which it sends to the amplifier.
An amplifier increases the volume of the sound and sends it to the receiver.
A receiver/speaker changes the electrical signal back into sound and sends it into the ear. Then those impulses are sent to the brain.
A battery provides power to the hearing aid.
Hearing Aids

17. Hearing aids aren't effective for everyone.
WHY NOT?
Hair cells in the inner ear must pick up the vibrations that the hearing aid sends and convert those vibrations into nerve signals.
So, you need to have at least some hair cells in the inner ear for it to work.
And, even if some hair cells remain, a hearing aid won't completely restore normal hearing.

18. What can people with hearing aids hear?

19. Cochlear Implants
Cochlear implants work better in people with more severe ear damage because they bypass the damaged parts of the ear and send the sound information -- as electrical signals -- directly to the auditory nerve.

20. The cochlear implant is made up of two main systems:
external system
three parts
a sound processor (2)
a microphone (1)
a transmitter (3)
internal system
two parts
a receiver (5)
an electrode array (6)

21. The microphone picks up sound and sends it to the sound processor, which translates sound into digital information.
It sends this digital information to the implanted receiver, which changes the digital information into electrical signals and sends these signals to the electrode array.
The electrode array sends these signals to the auditory nerve, which then passes along the signals to the brain.

22. The Cochlear Debate
Cochlear implants allow totally deaf people to hear common sounds such has a telephone, doorbell, car horn, and spoken voice.
In almost all people, understanding of speech is possible and lip reading is improved dramatically by the ability to hear the rhythms and the stops in normal speech.
Most people are able to talk on the telephone with modern cochlear implants.

23. However…
During the installation of a cochlear implant, all hair cells in the cochlea are destroyed.
Why is this a problem?
Damage of current hearing
Future technology

24. What can people with cochlear implants hear?