The Amazing Ear
How Our Sense of Hearing Works
By Banks A.
Science
September 2012

The ear helps us with many things. It tells us if there is danger or something nearby. If we couldn’t hear then how would we know what somebody else was saying? Well, in fact, if we couldn’t hear we couldn’t talk because we need to be able to hear ourselves speak or else we don’t know what we are saying! But humans have a horrible sense of hearing compared to many other types of animals. Dogs can hear way better than humans can, as can many types of predatory birds like hawks and owls. But this article is going to be about the human sense of hearing, though the ears of mammals and some birds are nearly identical to that of humans. Hearing is one of our five senses. For information on the other four, follow the links below:

Sight
Smell
Feel
Taste

The Outer Ear
The outer ear is the largest part of the ear and contains three main parts. The ear flap, also called the pinna, the ear canal, and the eardrum, also called the tympanic membrane. The sound is directed into the ear canal by the pinna and the ear canal then directs the sound to the eardrum, which then vibrates. The ear canal is filled with a waxy substance called earwax, which keeps dirt and dust from collecting on the eardrum. Dirt and grime on the eardrum can cause hearing loss. Sometimes small children will stick objects up their ears and burst the eardrum, causing immediate hearing loss in that ear.
ear anatomy being assulted by a pencil.jpg
Figure 1: A child sticking a pencil in his ear


The Middle Ear
The middle ear is the smallest division of the ear, only being about 1 centimeter long and 0.75 centimeters wide. It contains the three smallest bones in the body, the hammer, the anvil, and the stirrup. These bones transfer the vibration made by sound waves on the eardrum to the inner ear. The middle ear is connected to the inner ear through the round window, which is like the eardrum in function. The middle ear is connected to the throat by the Eustachian tube which opens when somebody yawns, coughs, of opens their mouth. In children a common cause of hearing loss happens when a fluid fills up the middle ear and stops the middle ear bones from vibrating. It can be cured by a surgeon making a small hole in the eardrum and letting all of the fluid drain out, and then he then patches up the hole.

The Inner Ear
The inner ear contains the cochlea and the beginning of the auditory nerve. The cochlea is a weird looking organ that looks like an up-side down snail shell. The inside of the cochlea is lined with sensing hair cells and a watery fluid. The cochlea picks up the vibrations from the middle ear bones through the round window. The vibrations cause the liquid in the cochlea to vibrate. The vibration of the liquid cause the sensing hair calls to vibrate which then convert the vibrations into electric impulses which travel to the brain via the auditory nerve.
ear anatomy 1.jpg
Figure 2: The anatomy of the ear



Hearing Loss
About ten percent of people in the United States live with some degree of hearing loss. There are two types of hearing loss, called conduction deafness and nerve deafness. Conduction deafness is caused when the ear canal is clogged and when the eardrum is popped or inflamed. Nerve dearness is caused when the cochlea or the auditory nerve stops functioning. People with conduction deafness can usually be helped with hearing aids and surgery but people with nerve deafness have little hope. But people that have a non-functioning cochlea do have hope. It is called a cochlear implant.

Helping the Deaf Hear
The first device that comes to mind when you think of helping people with hearing loss is the hearing aid. The hearing aid helps people with conduction deafness by making sounds louder, so that the ear can pick it up better. The first hearing aids were just simple cones made of wood or brass. The first true hearing aids were invented in the U.S. in the 1920s. They were in a pouch worn on the body and connected to the ear by a wire. The first modern hearing aids were invented in the 1950s. They were the first to be able to put inside your ear. But there was little help to people with a bad cochlea until the 1970s, when the cochlear implant was invented. A surgeon would insert a wire into the cochlea and connect that to an external microphone. The microphone would be connected to the “new” cochlea through wires and two other devices, the
cochlear implant.jpg
Figure 3: a diagram of a cochlear implant
internal receiver and the external receiver. The external receiver would send the information from the microphone to the internal receiver which then sends the information to the “new” cochlea via a wire. After that point the impulses were sent to the brain just like a person with normal hearing. Only about 60,000 people in the world have cochlear implants, but the number is growing at a steady pace. The technology that helps the deaf hear again is advancing rapidly and new devices come out every year.


Conclusion
Hearing is an almost essential sense that helps us comprehend the world around us. Without hearing we would clearly not be where we are today. Many things depend on hearing such as verbal speech. Think about what sounds effect your day. The alarm wakes you up; your mom’s (or dad’s) yells tells you that it is time for breakfast, lunch, or dinner. A car horn lets you know if somebody doesn’t like you (or your parent’s) driving and a dog bark means that there is a dog nearby. Hearing is a sense that people who have it can’t imagine living without and people who can’t hear don’t have any idea what they are missing.

Glossary
Auditory Nerve: the nerve that connects the ear to the brain. The auditory nerve ceasing to function is one of the most common causes of deafness.

Eustachian tube: a small tube between the middle ear and the throat. Its purpose is to relieve the pressure in your middle ear and to drain fluids from the middle ear.

Implant: an object that is inserted into a living organism for medical purposes.

Inflamed: It is the medical term for swollen.

Membrane: a thin skin-like substance that is usually stretched tightly between several points.


Citations:
“ear." Compton's by Britannica. Encyclopædia Britannica Online School Edition. Encyclopædia Britannica, Inc., 2012. Web. 24 Sept. 2012.

"Eardrum." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 15 Sep. 2012. Web. 25 Sep. 2012. Encyclopedia, 20 Sep. 2012. Web. 24 Sep. 2012.

Landau, Elaine. The Sense of Hearing. New York, Children’s Press, 2009. Print.

May, Mike. Sensation and Perception. New York, Chelsea House, 2007. Print.

Steele, Philip. The Five Senses. Englewood Cliffs NJ, Silver Burdett Press, 1988. Print

Wikipedia contributors. "Hearing (sense)." Wikipedia, The Free Encyclopedia. Wikipedia, The Free EWikipedia contributors.