Could be any number of things vibrating: Try shifting the PC case around a little. Sometimes that's enough to stop a vibration noise. See if you can pinpoint the source of the noise. Hold a cardboard tube, like from inside a roll of paper towels, up to your ear and point the other end in various directions inside the case. If it is the PSU fan, the only fix will be to replace the PSU.
Hi, I have a Dell Inspiron 5680 since around June 2018. I had heard these noise in the past few months. I thought it was the CPU fan or the rear fan but it is not. I opened the case and when it was making that sound, I placed my hands on the power supply and I could feel something. But when the noise stopped, it stopped too. Do I have to be worried about the machine and do I have to change the power supply unit. It still works, but just make this noise. Link To Video  Thank you.
Inspiron 5680 Power Supply Making Loud Noise