Dell XPS 9550 - Black screen + buzzing noise?

I bought my 9550 (i5/4k/256gb/8gb) on Feb 6 from the Microsoft Store. It suffered from some black screen issues, even after updating everything fully, BIOS, Intel/Nvidia drivers etc.

The past week, a new development has occurred. The laptop goes to black screen and a loud buzzing noise emits from the speakers. It's not the usual coil whine but a really loud buzzing sound. This happened once when I was watching a short video on Facebook, and again when I was watching a video on Youtube, both times using the laptop's speakers. It has crashed to a black screen before while watching YT but without the buzzing noise (I was using headphones), this is new.  I have checked that everything has been updated, and it has, yet this is happening. 

I'm past my return date, and surely all the force shut-downs I have to do because of the black screen can't be good for the laptop. I hate that I can't even watch a video without fear of my laptop black screening and making me force reboot. Why should I have anxiety over using something I just bought and paid so much for! Really frustrating laptop. Just another problem on top of all the others it has had.