Mini noise

I've had my Mini (Late 2012, 2.3, i7, fusion drive) a couple of weeks now and I love it.

One thing, though. I hear a slight buzz from the Mini when I, for example, move to a website in Safari, or scroll down my inbox in Mail.

I know sounds are hard to describe, but a low-volume short buzz is how it seems to me. It's not loud, but it's there. I'm assuming it's some kind of disc noise. I'm moving on from an old iMac, and I don't recall any particular disc noises from that.

You know how it is when you have a new machine and you're hyper-sensitive. So, is it normal?