I hear a quiet, low vibration in the case, which comes and goes. I heard this before, and posted a thread before on here. The conclusion was a bad power supply, which is no shocker because it was a very low-quality unit. I replaced it with a new one (https://goo.gl/PFjTcq). This resolved it until now. I bought this additional 2TB drive on a Newegg Flash sale. What could this be? I don't really care about unless it is damaging the drive.
Specs via PCPP: https://pcpartpicker.com/b/nW8Ycf
Specs via PCPP: https://pcpartpicker.com/b/nW8Ycf