How We Hear: A Quick, Simple Guide 

This blog post was written by Andrew Jenks, All Classical Radio and ICAN 2025 Intern.

An abstract visual that shows layers of blue sound waves, with a black background. 

Imagine you’re in outer space, where there is no air. Would you hear anything?  

In space, there’s no sound. Even if two nearby asteroids collided, you wouldn’t hear a thing. It’s dead silent. That’s because sound requires something to move through, whether it’s air, water, or something else. In other words, sound doesn’t just exist by itself.  

That said, scientists can “listen” to space using light, but that is a topic for another time. Here, we will only talk about regular sounds on Earth. 

Astronauts have air in their spacesuits, allowing them to hear their devices. Otherwise, they wouldn’t even hear themselves breathing. Pure silence can feel strange, since our brains aren’t used to it.  

On Earth, we hear things because of air particles. We can also hear underwater. Something vibrates, like a speaker cone, which causes a wave of energy that affects air particles. However, that would sound a lot different underwater. 

A speaker cone vibrates back and forth super-fast. This pushes air particles around like this: 

A diagram showing the process of a sound wave moving from a speaker to a human ear, showing that sound is generated by varying densities of particles. 

Each time it moves backward, it basically pulls the air particles towards it. When the speaker moves forward, it pushes the particles away. To play music, the speaker must move forward and backward incredibly fast. 

Wait a minute, how do the particles get affected like that? The speaker isn’t touching them directly, so how can the speaker make the particles move? Well, air is a gas. In a gas, particles want to spread out evenly. Any area of too many or too few particles will even out fast. 

When the speaker cone moves backwards, it creates sort of an “empty” space for the particles to move towards. When the speaker moves forward, it pushes (or compresses) the particles. This compression leads to a dense area of particles, which quickly gets spread out again.   

Think of it like spreading an even layer of peanut butter on your sandwich. You don’t want a big clump of peanut butter in just one spot! Particles in a gas also naturally want to spread out evenly. 

How do you hear? This back-and-forth motion makes a sound wave, which travels through the air. This causes your eardrum to vibrate. There are tiny bones in your middle ear, which vibrate in response to the eardrum. Why do we have these tiny bones? Their purpose is to amplify (make louder) the sound coming in.  

The reason the sound must be amplified is because, otherwise, the signal would be too weak for your brain. This is kind of like how a pre-amplifier device works. A pre-amplifier takes a very weak signal and makes it louder. This is often called pre-amp, for short.  

Why is the signal so quiet? This is because when a soundwave hits your ear drum, there is a huge loss of energy. Your eardrum is basically changing sound into a different form, so you can hear it.  

After the signal is amplified, it is sent to your cochlea. 

A diagram of the human cochlea, demonstrating the snail-like shape and the location of the oval and round window. 

The snail-shaped cochlea is one of the most amazing organs in the human body. It can analyze high pitch and low pitch sounds, then turn them into electrical signals. Waves move through the cochlea, which is picked up by tiny hairs. These hairs lead to the release of special chemicals in the brain which then generate electrical signals. 

This is why it is especially important to protect your ears. These little hairs are delicate and must be present for hearing to occur. If damaged, they don’t come back.  

In summary, sound must have something to travel through. Sound waves happen because particles are being pushed around by something vibrating. When a sound wave gets to your ear drum, the vibrations are then amplified by small bones in your ear.  

Then, the vibrations are sent to the cochlea, which interprets the high and low frequencies. The tiny hairs in your cochlea pick up on the waves and trigger electrical signals. Your brain then tries to make sense of what it’s hearing.