Have you ever learned the lyrics of a song by heart, only to realize later that you were singing some of the words wrong? Hearing can seem to be the most fickle sense—the sound we think we hear isn’t always the sound that entered our ears, creating a recipe for miscommunication.
Like all senses, hearing involves a partnership between a body part—the ears—and the brain. It’s a complex system with many components that have to work together to interpret sounds accurately. It’s also one of our most treasured senses–it lets us communicate and connect with other people. While we can also “talk” through written text, there’s no substitute for hearing another person’s voice.
How does hearing really work? Let’s delve into the inner workings of the ear and brain to find out how this sense keeps us connected to each other and the world.
First, Sound Meets Your Outer Ear
When something makes a sound, that sound travels through the air in the form of sound waves, or vibrations. Then, those vibrations hit the outer part of our ear, which is where hearing begins.
The shape of the outer ear helps capture the sound, sort of like a funnel for these air vibrations. Animals with cup-shaped ears larger than ours can hear even better than we can because their ears do a better job of catching sounds. Your outer ear is also known as the auricle, or pinna.
Next, Sound Travels Through Your Middle Ear
After the outer ear captures a sound, the sound waves travel into the middle ear where the eardrum is located.
To get to the eardrum, sound moves through the ear canal, which you’re probably most familiar with as the source of earwax. Earwax might seem dirty, but it actually exists to keep your ears clean— it blocks dust, debris, and microorganisms from entering the ear. It’s best to avoid removing earwax with Q-tips or other tools, as that can push the earwax into the ear canal and temporarily block your hearing.
Thanks to earwax, sound can travel safely through the ear canal, while undesirable things are blocked from entering the eardrum. The sound waves then cause the eardrum to vibrate. Your eardrum is a thin layer of tissue, also known as the tympanic membrane, and serves as the barrier between the outer and middle ear.
From the eardrum, sound waves get transmitted to three little bones in your middle ear, called the auditory ossicles. You may have heard them referred to as the “hammer,” “anvil,” and “stirrup” due to their shapes. These bones amplify the sound as they vibrate.
The vibration enables the sound to keep traveling further into the ear.
Then, Sound Reaches Your Inner Ear
Now, the sound has reached your inner ear, where the cochlea is located. The cochlea is a spiral-shaped tube that looks like a snail shell.
Although tiny, the cochlea is complicated, involving many minuscule parts that work together to help translate sounds. For example, it contains hair cells that differentiate between high-pitched and low-pitched sounds. The cochlea is also responsible for the complex process that turns sounds into electrical impulses, which can then be sent to the brain.
Finally, Your Brain Makes Sense of the Sound
From the cochlea, the electrical impulses representing the sounds you’ve just heard travel through the auditory nerve to reach your brain.
Each sense gets processed in a different part of your brain. For sound, processing happens in the auditory cortex. The auditory cortex enables us to figure out what a sound means, where it comes from, and what produced it.
Of course, this process is imperfect, and we don’t always interpret sounds correctly. Still, overall, our brains do a remarkably good job of figuring out what we’ve just heard—-or getting close enough to the right answer.
While our sense of hearing is remarkable, there are also many sounds in the world that we can’t hear, like the high frequencies you might notice your dog responding to when you can hear nothing. But the animal with the best sense of hearing in the world might surprise you—-it’s actually the greater wax moth. While we often use hearing for communication and navigation, it’s a matter of life or death for moths: their sensitive hearing enables them to detect and avoid predatory bats using echolocation.