THE OUTER EAR
When we think of our ears, we generally think of the pinnae, which are the visible protrusions of our ears. Some of us may have large ears, others small, but they all serve the same function: to collect the sounds around us and transport them to the inner ear where they are sent as signals to the brain. The shape of our ears is ingenious—the curves of the outer ear, which are made up of cartilage, are not simply decorative, they serve to funnel the sounds in the atmosphere into the ear canal. The ear is actually much more than what is visible to the eye.
How sound is Made and Carried
To understand the function of the ears, we should take a moment to discuss how sound is created and how it travels. Sound waves are the result of vibrations that travel through our atmosphere - basically the bumping together of particles of matter through the collision of air particles.
Wherever the vibration is made, the sound will be carried, even in water or in earth.
The speed of the vibrations created by an object which is emitting sound, make a difference in the pitch of the sound we are able to hear. A high pitched sound is the result of very quick vibrations; and a low pitched sound, conversely, is the effect of slow vibrations. These sound waves are picked up by the outer ear and channeled into the interior components of your ear.
Designed for Hearing
Humans have pinnae (the outermost part of the ear) which point forward and have a myriad of curves that catch the sounds that are traveling all around us. Unlike other mammals, human beings cannot move their ears in the direction of sounds. If you have a dog, you have probably seen him perk up his ears and turn them to the side and forward again, attempting to find the source of the noise. Predatory animals as well as their prey use their ears to hunt and to hide, respectively. Human ears are positioned more for communication than for hunting, but you can augment your ability to hear by cupping your hand behind your ear, and this channelizes the sound more effectively. If you have larger than average ears, take heart - you actually hear better than your smaller eared friends, because your large pinnae can collect more sound than smaller ones!
Our brains are able to interpret the distance and placement of sound because of the way the sounds reach our outer ears. A sound that is coming from the front of you will be collected and channeled, and then translated differently from those sounds that are coming from behind your back. You are able to place the sound horizontally - whether it is coming from the left or right because the sound waves will actually reach the respective ear faster. If your son is calling you and he is standing to your left, the vibrations he is creating will hit your left ear before they make it to the right. The information that gets transferred to the brain will alert you that the sound is coming from your left side.
The Ear Canal
Measuring roughly an inch in length and about ¼ inch in diameter, the ear canal carries the sound that is captured by the pinnae into the middle ear - to the eardrum. The canal is funnel shaped and sloped to ensure that no water is collected close to the eardrum under normal conditions. It is sized and shaped for maximum efficiency in delivering sound to the middle and the inner ear, and also to keep the area free from infection.
Earwax
Earwax, also known as cerumen, is produced in the outer part of the ear canal to lubricate and clean the interior part of the canal. Earwax should not cause problems for most people as it helps to rid the ear canal from dead skin cells. Earwax also defends the ear against dirt and infection. Many people resort to using cotton swabs to remove earwax and actually end up doing more harm than good when they push the wax back into the ear canal towards the eardrum. When it comes to wax, a hand off approach is best and you should never put anything into the ear canal.
THE MIDDLE EAR
The Eardrum
As sound waves travel down the ear canal, they will quickly move through the outer ear and hit what we generally refer to as the eardrum. This tympanic membrane separates the outer ear from the middle ear and serves as the sensory component of the ear. This tiny membrane is not even half inch in size, but it is constantly working and responding to the many air fluctuations that occur in the atmosphere. Every sound wave that enters the ear canal through the outer ear will hit the ear drum and cause a reaction.
The stiff and rigid piece of skin will be pushed back and forth by the air particles of sound in relation to their pitch, volume and even distance. A high pitched sound will vibrate the tympanic membrane very quickly; a loud sound will vibrate it for longer intervals to represent the intensity of sound. The eardrum is the beginning of the interpretation of sound waves into information for the brain to process.
In situations where there are competing levels of sound, the eardrum will help you to focus and concentrate your hearing on higher pitched sounds, and essentially drown out the louder and lower pitched sounds.
This would come into play if you are on the playground with your kids and you are trying to carry on a conversation with your friend. Your eardrum helps you zero in on what your friend is saying and relegate the playground noise to the background. When auditory conditions are less than optimal, the eardrum will actually protect you from loud and harmful noises. A very loud low pitched sound will cause the tympanic muscle to contract sharply and not vibrate in its normal way, thus lessening the amount of sound that will travel to the brain.
The Ossicles
So far, sound waves have traveled through the air. First, a sound was collected by the pinnae and pushed into the ear canal; second, the eardrum reacted to that sound by vibrating according to the pitch and volume. The next section of the middle ear will do the work of amplifying that sound so that when it reaches the fluid of the inner ear, it can stand up to the increased inertia that awaits it. The Ossicles are a series of bones that react in conjunction with the vibrations created by the eardrum. If you can imagine a set of dominoes - with each one tipping over the next, you will have some idea of how these bones work in conjunction with each other to transfer the vibrations from the ear drum into the inner ear.
As we have already discovered, the middle ear is an air filled space that is occupied by three tiny bones: the malleus, the incus and the stapes. Commonly referred to as the hammer, the anvil and the stirrup respectively, these bones, although very small, do the big job of moving sounds into the inner ear. When the eardrum vibrates, it transfers that energy to the malleus, which is actually connected to the eardrum. The malleus moves back and forth, side to side; and this in turn moves the next attached bone, the incus. The incus takes that energy and transfers it to the stapes. The stapes is positioned to impact the cochlea, which make up the fluid filled chamber of the inner ear.
Amplification takes place in the middle ear because the bones are perfectly designed to work together, and their interaction increases the forces of pressure on the cochlea as they bump up against each other. The size of the eardrum in comparison to the size of the bones helps this amplification process. Because the eardrum is larger than the Ossicles, the energy can be actually multiplied as it is conducted through these bones. The smaller parts sustain a greater impact, and therefore pass on more energy to the next component than the eardrum would on its own.
The Eustachian Tube
Anyone who has ever suffered a head cold knows that the ears are connected to the nose, and this connection occurs in the middle ear through the Eustachian tube. A small tube leads from the middle ear to the Nasopharynx. The tube supplies the counter-pressure of air to the eardrum, making the air pressure on both sides of the small drum equal. It also helps to clear the middle ear of congestion and in doing so, prevents any infection. If you have felt the sensation of popping in your ear, it is the effect of air pressure on the Eustachian tube versus the exterior pressure of the ear canal.
When you yawn, chew or swallow, you usually hear a small clicking sound in the ear - this is the pressure equalizing between the Eustachian Tube and the ear canal. If you have flown in a plane, you may have experienced popping and clogging of your ears - maybe you chewed gum or tried to yawn to rid yourself of this annoying sensation. You were letting the interior pressure that is provided by the Eustachian tube through the Nasopharynx to rise to an equal level with the exterior pressure that was passing into the ear canal. If this cannot be achieved, as is the case with a person who flies when he or she has a cold or sinus congestion, it can be very painful and can even cause the eardrum to burst.