One of the Five Senses; Hearing

Mhairi Robertson, Olivia Shin & Jacky Tse

Hearing is a special sense that works differently from how we process our other senses. While other senses require chemical reactions, hearing is a mechanical process. Hearing is still very mysterious because the way the brain interprets the sound signals is very complicated. There is still a lot to be learned about how we hear. However, we do know quite a lot about how the inside of our ears work.

The ear is comprised of three main parts; the inner ear, the middle ear and the outer ear. By working together these three areas protect each other and allow us to hear sound. The most outer part of the ear or the pinnae catches sound waves and helps draw them into our ear. We can determine where noise is coming from because of the way it bounces off the pinnae. As sound waves enter the outer ear they go through an area called the ear canal or tympanic membrane. Here, the sound waves are amplified making it easier for us to distinguish complicated sounds like speech.

The sound vibrates the ear drum which is a tiny piece of skin that flaps when sound waves hit it. Interestingly, when the ear drum senses a loud noise a muscle pulls the ear drum taut stopping the sound from damaging the inner ear. When the ear drum moves it vibrates the ossicles– the three tiny bones inside your ear. Ossicles are located in the middle ear and are commonly referred to as the hammer, anvil and stirrup. These bones amplify the sound one last time before they enter the inner ear.

Once inside the inner ear the sound waves travel through canals filled with water. It is harder for sound waves to move through water, hence why the sound is amplified by the other elements in the ear. This watery area is called the cochlea and looks like a spiralling shell. The sound waves cause the water to move which stimulates tiny hair cells in the cochlea. These tiny hairs send electrical messages through the auditory nerve to the brain. How the brain interprets these signals is still a mystery.