2. Hearing is one of the five human senses.
Hearing | Sight | Smell | Taste | Touch

3. How We Hear We use our ears to hear sounds.
Sounds travel through the air and our ears as sound waves.

4. How We Hear
Sound waves are collected by the outer part of the ear, called the pinna.
The pinna is the only part of the ear that you can see with your eye.

5. How We Hear
After the sound waves are collected by the pinna they are sent through the ear canal before reaching the ear drum.
When the sound waves hit the ear drum, it vibrates.

6. How We Hear
The vibrations from the ear drum make three small bones in the ear vibrate.
The hammer
The anvil
The stirrup
Those three bones together are called the ossicles.
stirrup
anvil
hammer

7. How We Hear
The vibration of the ossicles transfer the sound waves to the inner ear.
The inner ear has two parts, the cochlea and the semicircular canals.
The semicircular canals. help you determine movement and to stay balanced.
semicircular canals
cochlea

8. How We Hear
As the sound waves pass through the cochlea, they cause microscopic hair cells to vibrate.
These hair cells, called cilia, are linked to the auditory nerve. When the cilia vibrate they send an electric impulse signal to the brain.
When the signal reaches the brain, we hear!
auditory nerve
cochlea
Cilia
From David J. Lim. Functional Structure of the Organ of Corti: A Review. Hearing Research, 22 (1986)

9. How We Hear
As the sound waves pass through the cochlea, they cause microscopic hair cells to vibrate.
These hair cells, called cilia, are linked to the auditory nerve. When the cilia vibrate they send an electric impulse signal to our brain.
When the signal reaches the brain, we hear!
auditory nerve
cochlea
Cilia
From David J. Lim. Functional Structure of the Organ of Corti: A Review. Hearing Research, 22 (1986)

10. Now imagine not being able to hear your friends and parents talk.
That’s Hearing Loss!

11. NIHL (Noise-Induced Hearing Loss) Hearing loss as a result of prolonged or sudden exposure to loud noise.
When we are exposed to noises that are too loud, our tiny hair cells in the cochlea vibrate too hard.
The vibrations cause them to break and bend.
From David J. Lim. Functional Structure of the Organ of Corti: A Review. Hearing Research, 22 (1986) Elsevier

12. NIHL
Once our microscopic hair cells bend and break, they will never be straight again.
There is no surgery to fix the hair cells, once they are damaged they will never work properly again. 
To treat NIHL visit an audiologist.
From David J. Lim. Functional Structure of the Organ of Corti: A Review. Hearing Research, 22 (1986) Elsevier

13. Audiologist An audiologist is the person you visit to
have your ears checked.
He or she will look inside your ears to make sure everything looks alright
He or she will do a hearing test to make sure you are hearing everything alright.
If the audiologist finds that you have hearing loss, he or she will
work with you to select and fit hearing aids so you can hear again.

14. Noise levels or loudness are measured in decibels (dB).
Any loud noise over 85dB is considered loud enough to cause NIHL.
90 dB A hair dryer, or lawn mower
100 dB MP3 players at full volume
110 dB Concerts and sporting events
130 dB Ambulance
30 dB Whisper
60 dB Normal conversation or a dishwasher
70 dB A vacuum Cleaner
80 dB Alarm Clock

15. Levels of Noise chart.

16. 3 Ways to Protect Your Hearing

17. Walk Away If the noise around you is too loud, walk away.
Moving back 10 or 15 feet from the noise can make the noise going into your ears less loud.
If you are in a noisy place, make sure you only stay for 30 minutes, if you are not wearing any ear protection.

18. Turn It Down
When TVs, car stereos, and MP3 players are turned up too loud, the noise can hurt your ears.
Turn down the volume to protect your ears.
Keep the volume at 50%.
When listening to anything with ear buds or ear phones, if someone next to you can hear what you are hearing,
the volume is probably too loud.

19. Wear Ear Protection
If you know you are going to be in a loud area with noise over 85 dB, wear ear protection.
Earplugs
Custom (made to fit your ear) earplugs
See an audiologist for these, similar to what musicians and pilots wear.

20. If you think you or someone you know might have a hearing problem, tell your parents to go online to to find an audiologist near you. Questions???