Joan Cartan-Hansen, Host: Hearing is one of your five senses.

It's called the auditory system and it does more than just take in sound.

So listen up.

(Music) Student one: Would you like a drink of water?

Student two: What?

Student one: (louder) Would you like a drink of water?

Student two: What?

Student one: You can't hear me if your music's too loud and besides, that's bad for your hearing.

Student two: Why?

Student one: Because loud sounds can damage your ears.

Student two: How?

How does your hearing work?

Cartan-Hansen: Hearing begins with sound.

When you make a sound, you create energy in the form of sound waves.

A loud sound (loud thud) has taller waves than a (page turn) soft one.

Those sound waves eventually enter your ears.

The sound travels down the ear canal.

The ear canal is about an inch long and at its end is a thin piece of skin called the eardrum.

The eardrum is stretched tight, just like the top of a drum.

When soundwaves hit the eardrum, it begins to vibrate.

That vibration makes three tiny bones in your middle ear begin to move.

These three tiny bones are known as the hammer, anvil and stirrup because that is kind of what they look like.

These three bones transmit or move the sound along to the inner ear.

They also increase the force of the soundwaves.

Soundwaves then move into a snail-shaped structured in the inner ear called the cochlea.

The cochlea is filled with fluid and more than 17 thousand tiny hair-like tissues called hair cells.

Soundwaves move through the fluid and the hairs cells bend.

The movement of those hair cells stimulates the 30 thousand nerve fibers leading to the hearing nerve.

That nerve carries the signal to the brain.

And the brain figures out what the sound is.

It's important to protect your hearing from loud sounds.

Muscles in the middle ear protect the ear by stiffening the ear drum and the movement of the hammer, anvil and stirrup bones.

But sudden loud sounds can break and damage the hair cells in the cochlea and can even break the eardrum.

And continued loud sounds can also damage those tiny hair cells.

So be sure to wear hearing protection like earmuffs or ear plugs if you are going to be around loud sounds and turn the volume down on your headphones.

Because once your hearing is damaged, it can't be made all better.

About two hundred thousand Americans are deaf.

That means they can't hear anything.

Another three million have severe hearing problems.

They use hearing aids to amplify or increase the strength of sound waves so they can hear better.

Others have a cochlea implant.

That's where a small microphone helps transmit sound to the hearing nerve.

Individuals who are deaf or hard-of-hearing sometimes use sign language to communicate.

Others can read lips.

Communicating, whether it is with your ears or your hands is essential to life.

And you need two ears to figure out where a sound is coming from.

Your brain figures out the difference between the two sound levels in each ear and calculates where the sound is coming from.

Oh, by the way, your ears do something else.

Another part of the inner ear is called the vestibular system.

Movement of the fluid inside the vestibular system tells your brain about your body position and the direction that you are moving in.

That way you can tell up from down, even with your eyes closed.

And when you spin around, the fluid in the vestibular system spins too.

That fluid keeps moving for a bit even after you've stopped and that explains why you feel dizzy.

Student two: Wow, I didn't know our auditory system was so important.

I'll pay more attention to my hearing.

Oh, I'll have that water now.

Student one: Oh sorry, I didn't hear you.

Cartan-Hansen: If you want to learn more about hearing, check out the science trek website.

You'll find it at idahoptv.org/sciencetrek.

(Music) Announcer: Presentation of Science Trek on Idaho Public Television is made possible through the generous support of the Laura Moore Cunningham Foundation, committed to fulfilling the Moore and Bettis Family legacy of building the great state of Idaho; by the Idaho National Laboratory, mentoring talent and finding solutions for energy and security challenges; by the Friends of Idaho Public Television; and by the Corporation for Public Broadcasting.