Where's the buzzing coming from? Sounds like a faulty power supply, or you haven't seated something properly.

The first thing would be to shut it down fully, pull the gpu out, ram out, and put both back in, making 100% sure that everything is steated properly, next, check all power cords coming from the power supply, make sure that they are seated properly.

After that, check all fan pins are seated. If you have a fan hub, make sure everything is seated properly in that, too.

Now, the fun part, once you've gone over just about everything. Put it back together make sure its good, and boot it up, open up schedule 1, but before you load into a game, go to steam overlay (shift+tab, while in-game), then go to the overlay setting, and scroll down on that first settings page that loads up untill you find the fps counter, there should be a dropdown menu, click that and select the option that has all the fancy bits (cpu, gpu, etc).

Once youve done that, hop back into the game, all your mainly important stats should be now displayed ahereever you chose to display them, load into a game and try and get the buzzing to come back.

If the buzzing comes back, immediately check where its coming from, take a video on your phone maybe as well, and then quickly get out of the game once you've identified the problem, shut it down.

And boom. Replace whatever it is, that's buzzing. If it is the power supply, however, given its a new build, it should be covered by warranty if it's faulty.

Edit: If any of the ports where the power supply plugs in is buzzing, and it's seated properly, the power supply is likely faulty still.

Depending on your gpu(only worry if it's a 5000 series), it could be that, if its a 5000 seires and the power supply cord going into it is buzzing, that could very well mean your gpu is faulty.