Given the task definition and input, reply with output. In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 

The outer ear collects sound waves. The sound waves travel from the outer ear to the middle ear. The eardrum changes the sound waves into vibrations. The hammer, anvil, and stirrup bones vibrate. The sound moves to the inner ear. The sound enters the liquid-filled cochlea. The cochlea vibrates. Small hairs in the cochlea move. Nerve signals are created. The brain understands the nerve signals as sound. 

sound waves ,vibrations ,sound ,nerve signals 