Hard drive noise in desktop

Is it common for you to be able to hear the hard drive a little bit in an AIO? My dad has an AIO also but you can't hear the hard drive at all in it. Only if you're really close to it. I noticed that the hard drive is on the right side, right under the optic drive. The hard drive isn't covered. It's in the open. I can see my hard drive due to there being something that looks like a vent. I...