When sound waves reach your ear, you know you've heard a soft sound or a loud sound. The sound passes through the outer ear and is funneled into the middle ear, where it bounces off the ear drum and is amplified through three tiny bones: the hammer, anvil, and stirrup. These are the smallest bones in your body. Together they are smaller than an orange seed. It then travels into the inner ear, which is filled with fluid, through the cochlea, and passes the vibration of the sound through the hair cells to your brain.