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Posted by on Nov 3, 2015 in TellMeWhy |

How Do We Hear Sounds?

How Do We Hear Sounds?

How Do We Hear Sounds? When sounds are made, they set up movements in the air. These movements are called sound waves. The cup-like shape of the outer ear collects the sound waves. Then the waves travel inward to your eardrum, a thin piece of skin like the head of a drum.

When sound waves hit the eardrum, they cause it to vibrate, and three tiny bones in your ear move with each vibration.

These bones in turn cause vibrations in a fluid that fills the inner part of your ear. The fluid presses on your hearing nerve cells, which pass the sound message to the hearing center in your brain.

The ear is made up of three different sections: the outer ear, the middle ear, and the inner ear. These parts all work together so you can hear and process sounds.

The Outer Ear

The outer ear is called the pinna or auricle. This is the part of the ear that people can see. The main job of the outer ear is to collect sounds, whether they’re your friend’s whispers or a barking dog.

The outer ear also includes the ear canal, where wax is produced. Earwax protects the canal. Earwax contains chemicals that fight off infections that could hurt the skin inside the ear canal. It also collects dirt to help keep the ear canal clean.

The Middle Ear

After sound waves enter the outer ear, they travel through the ear canal and make their way to the middle ear. The middle ear’s main job is to take those sound waves and turn them into vibrations that are delivered to the inner ear. To do this, it needs the eardrum, which is a thin piece of skin stretched tight like a drum.

The eardrum separates the outer ear from the middle ear and the ossicles, which are the three tiniest, most delicate bones in your body. They include:
• the malleus, which is attached to the eardrum and means “hammer” in Latin
• the incus, which is attached to the malleus and means “anvil” in Latin
• the stapes, the smallest bone in the body, which is attached to the incus and means “stirrup” in Latin

When sound waves reach the eardrum, they cause the eardrum to vibrate. When the eardrum vibrates, it moves the tiny ossicles — from the hammer to the anvil and then to the stirrup. These bones help sound move along on its journey into the inner ear.

The Inner Ear

Sound comes into the inner ear as vibrations and enters the cochlea, a small, curled tube in the inner ear. The cochlea is filled with liquid, which is set into motion, like a wave, when the ossicles vibrate.

The cochlea is also lined with tiny cells covered in tiny hairs that are so small you would need a microscope to see them. They may be small, but they’re awfully important.

When sound reaches the cochlea, the vibrations cause the hairs on the cells to move, creating nerve signals that the brain understands as sound. The brain puts it together and you hear.

Content for this question contributed by Lee Fahllrish, resident of Cincinnati, Hamilton County, Ohio, USA