How Hearing Works - Naperville & Wheaton, IL
Anatomy of the Ear
1. Ear Canal
2. Tympanic Membrane
6. Oval window
7. Eustachian Tube (canal leading to the nose )
9. Auditory Nerve
Hearing may seem simple, but your ears are incredibly complex structures that allow you to detect and localize all the sounds around you. Sound waves in the environment reach the outer ear, which directs sounds to the middle ear. The vibration of the middle ear cause movement in the fluid-filled inner ear, where the cells in the inner ear sense this movement, translate the sound waves into electrical impulses, and send these signals to the brain.
The Outer Ear
The part of the ear we can see is the outer ear, or pinna. The grooves of the outer ear aren’t for show, and they direct sound waves into the ear canal while amplifying sounds in the 2000 to 3000 Hz range, making it easier to understand speech.
The ear canal is also part of the outer ear, and the thin layers of skin around the ear canal increases blood flow to help you hear. The ear canal is also lined with ear wax, or cerumen, which traps dirt, dust, sweat, and moisture before it can reach the middle ear.
The Middle Ear
The first structure of the middle ear is the ear drum or tympanic membrane. It separates the outer ear from the fluid filled middle ear, and this thin membrane is composed of three layers. When sound waves reach the middle ear, they cause the tympanic membrane to vibrate, and this vibration moves the three tiny bones behind the ear drum. These bones, called the ossicles, link the middle ear to the inner ear, and they transmit the vibrations from the tympanic membrane to the inner ear.
The middle ear also has a sophisticated air pressure equalizing system. The eustachian tubes connect the middle ear to the back of the throat, and the tubes open when you swallow, yawn, or move your jaw. This structure is what allows you to pop your ears on a plane to relieve the uncomfortable buildup of pressure in your ears.
The inner ear is a snail-shaped organ called the cochlea. This fluid-filled organ is lined with tiny hair cells that allow you to hear. When the ossicles of the middle ear vibrate, the fluid in the inner ear moves, and the hair cells bend with the movement. They convert this movement into electrical impulses, and transmit these signals to the brain along the auditory nerve. The auditory center in the brain then interprets these signals as sound.
The inner ear also houses the semicircular canals. These structures are also filled with fluid, but they’re not involved with hearing. Instead, the movement of the fluid in these canals help you keep your balance when you move.