Hey guys, I bought my Xps 15 two week ago (I7 512GB 16GB 4K Touch screen) and had the same static sound problem so I returned it and changed one. Unfortunately, the new Xps 15 9550 still have the noise problem.

This morning l read all your posts and tried to solve this problem, When I  turned off the MaxxRadiao 's Speaker Enhancement , the Static noise disappeared. It has been 30 mins and l no more heard any sparking noise or static noise when I watched videos and streams. So l thought this might also worked for you guys.

Here is the solution: 

Double click Dell Audio and Turn off the speaker Enhancement.

If this also work for you , please let me know