Humming/vibration noise coming from HDD or case fan (video included in the post)

About a week ago i replaced my stock CPU and case fans with the following:

CPU: CoolerMaster Hyper 212x

2 case fans (front & rear): Be Quiet! Shadow Wings, Mid Speed

Everything was fine, until i realised i had installed the front case fan facing the wrong direction (exhaust instead of intake). I fixed that and then i started working on my PC again. I believe it was around that point when i first heard this humming noise, described perfectly by this guy here: http://www.tomshardware.co.uk/answers/id-2365923/wierd-noise-resonsance-freuenceny.html

I too couldn't locate the problem, as when i was going close to my PC case the noise would stop. For them, the problem was that they had their HDD upside-down, but i don't believe that's what is causing the problem in my case, as you can see in this video my HDD is installed correctly (the video also gives further information on the problem - it might help if you use your headphones):

https://streamable.com/0cx3y

I have noticed that for the noise to come up, both my HDD and front case fan have to be powered. When i disconnect one of those two from my PSU, the noise stops immediately!

The noise also stops, when i remove the front frame from my PC case.

No other of my SSD, CPU, GPU or rear case fan have any effect on the issue, either they are being powered or not.

I didn't try turning my HDD upside down. Should i try that, even if mine is installed correctly?

I really don't know what exactly is causing the problem and i am scared that might damage my PC if i keep ignoring it.

Thanks for your support!