The cochlea looks like a spiral-shaped snail shell deep in your ear. And it plays an important part in helping you hear: it changes sounds into nerve messages and sends them to your brain. After the eardrum takes in a sound, the sound gets turned into a vibration that travels to the cochlea. There, the tiny hairs that line the cochlea move and shake, sending messages to your brain that you hear a sound. And this all happens in a split second!