All vertebrates use the ear in the same way: to magnify waves of sound by transforming the waves into signals that the brain interprets. As a result, you are able to hear everything around you, from birds chirping to the voices of friends and family.
Sound works by traveling through air in waves. These waves compress, then stretch, and the process then repeats. The compression pushes on the tissue and, as the wave stretches out again, it pulls on the tissue. These pushing and pulling waves then cause a vibration.
The Ear’s Structure
Waves of sound first strike the outer ear (i.e., auricle or pinna). The outer ear’s shape assists in collecting sound and directing it with in the head. It then travels toward the middle ear and the inner ear. The ear’s shape allows the sound to amplify, which helps in determining where the sound is coming from.
Sound waves travel from the outer ear through the ear canal, which is only about an inch long, to the eardrum located inside the head. A tight membrane stretches across the ear canal’s end. When sound waves impact the eardrum, they cause a vibration in the membrane. This causes a triggering of pressure waves which then swell, passing into the middle ear.
Within the middle ear is a small cavity which consists of three tiny bones. Individually they are the malleus, which in Latin means hammer; the incus, which in Latin means anvil; and the stapes, which in Latin means stirrup, and as a trio they are the ossicles. This trio of bones work together in receiving sound waves and transmitting them along to the inner part of the ear.
The inner ear has a snail shaped structure that is filled with fluid. This is the cochlea. The cochlea contains ranks of microscopic hair cells which contain collections of small strands that are also like hair and are embedded in a membrane. When the vibrations of sound enter within the cochlea, they cause the membrane, along with its hair cells, to sway back and forth. The movements of these cells and the membrane send messages along to the brain.
Putting It All Together
A sound transmits in the form of sound waves from the environment. The outer ear collects these sounds waves and then send them down the ear canal until they strike the eardrum. The eardrum then which in turn sets into motion the trio of tiny bones, the ossicles, set within the middle ear. The bones’ motion then causes the movement of fluid in the cochlea or inner ear. This movement of the fluid in the inner ear, in turn, causes the cochlea’s hair cells to bend. The hair cells’ movement converts into electrical pulses. These electrical pulses then transmit to the auditory, or hearing, nerve and sent up to the brain. Once in the brain, the pulses are interpreted as sound.