Usually this question pops up as folk get a new PC. "It sounds different."
You can improve this with better mounting of the drive. I found years ago that putting a 3.5 inch drive in a plastic adapter to a 5.25 inch bay to really cut the noise levels.
Bob
hey, i was wonder if its normal for a 7200 rpm hard drive to make noise. You can usually hear it any were in the room it does not do it a lot but you can definitely hear it when it does. It is less than 6 months old, and there are 2 operating systems running on it. I runs really really fast.

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