Your ear has three regions: outer ear, middle ear, and inner ear. When sound waves enter your ear canal, your ear drum vibrates. The vibration moves three bones in your middle ear called ossicles. The ossicles are also called the hammer, anvil, and stirrup; they are tiny bones that transfer and amplify sound waves to the oval window behind the stirrup. When the oval window vibrates, fluid moves across a membrane inside your cochlea, causing the membrane to move. Specialized hair cells translate this movement into nerve impulses, which your brain interprets as sound.