Which noises made by the laptop's HDD are considered normal, and which shouldn't be?

Question

I got a replacement for a rather recent MacBook Pro 2012 model, which is the one that corresponds to the 15-inch screen, 2.3 Ghz Intel Core i7 processor. This new computer probably has around 3 weeks since I got it from the store. I have to clarify that I count only with the 1-year warranty, now.
My situation started after a couple of hours of getting it handed-over at the store where I got it from. We went through some really "sketchy" roads, before arriving home; firstly, roads covered with little rocks only, for about half an hour (it was a kind of middle-class suburb), and after that, we casually happen to visit roads one expects to encounter at a rustic town in Mexico. They aren't paved, but just land, with road bumps and potholes appearing quite oftenly. It's not a chaotic ride but not a very comfortable, pretty one either. So, one doesn't need to think excessively to get the picture of the car having been constantly shaking during that period of time (less than an hour), but on the other hand, the rest of the roads were of the normal-highway kind, smoother, before and after having visited those parts.
My worrying derives from the thoughts that refer to the possibilities of some kind of internal hardware damage or deadjustment, derived from all of that shaking part, to any of the movable components inside, particularly; not mattering how hidden or little, you know, if it could get me some problems eventually. It makes me wonder if the noises I hear all the time, coming from the hard drive, came from there, in comparison to the previous one I had and used; as if some component(s) could have deadjusted or something. Remember I said it was a replacement? Well, the previous one was much more silent when working, meaning, it didn't make those scratchy noises, but just the usual head-parking sounds as far as I perceived. It also means I now count with the 1-year warranty only, as I said before. For example, I can hear it in a "closed room" environment, which is silent enough to keep thinking about what is happening inside of the device you're using. I can also hear a kind of whirring or blowing sound, as from the HDD spinning (which is what I imagine, but I'm not sure of what it is exactly).
That's where the question comes in: Which HDD sounds are considered normal? How can I know them and differentiate them, in order to know if my laptop is O.K. or not? Could you describe the way you hear you MacBook working? Is there any program I can use to check it, beside the diagnostics mode included?
From all of this, I decided to run the AHT (Apple Hardware Test) more than once for my relief, but I'm not sure of its accuracy either. It showed no warnings. I need to know if it's enough with those tests to know if everything hardware-related is alright.
I don't want to get it checked from where I got it from, since it wasn't an exactly nice experience to get it changed and I can't be certain about wether the employees will help me good-heartedly. I haven't used the Apple Support phone number because I think the forums are a good option, so I trust your understanding. I look for more than "yes/no" answers, in other words, the "why", and a rather thorough response. I need to see you know what you're talking about, not just a guess. Thank you.

Answer 1

Here's an update. I just did the Disk Utility tests, of basically all the elements that appear on the left of the window (3 available selections), including the Macintosh HD one. They all passed the verifying and repairing processes, no warnings or errors whatsoever. Yay. The point is, yesterday I was looking at my photos from the Finder. I wasn't doing anything at all, really, not even moving the cursor, when I suddenly heard the HDD making the working-noise without stopping, just that constant scratchy noise. This went for something like 7 seconds straight, and at the very next moment, it started making a consecutive and tempoed stream of this same sound, but a little bit less intense, with interlapses of about a sec. This continued for about a whole minute. I'd like to know if things are really fine.
As I previously described, the guys at iShop almost don't want me there anymore, or at least that's what their distanced attitudes get my into thinking. I visited the place some days ago, to look at the new iPod Touch pretty quickly, and I clearly felt that the guards were watching me closely, you know, with a hostile mannerism, the kind of stance that you use, with arms folded, to look kind of intimidating. I really didn't do anything to deserve that paranoic and ridiculous behavior. What happened was, a bit hottened discusion with the manager, when I was telling him I needed a replacement, and he really wasn't giving me an empathetic and understanding attitude.
If a call to Apple Support is required soon, and my computer needs to be repaired or the HDD replaced, they'll most likely send me there, since it's the most prominent place of recommendation. Sincerely speaking, they do seem like the most prepared personel, and they aren't great per se. If that is so, I really, really hope that the hard drive is the only part or detail that needs some technical considering, and deserves my stress.
Thanks for your consideration, so far so good.