I had the same problem with the buzzing sound which was driving me plum crazy! I turn up ZZ top loud and the buzz bout blowed my ear drums out. It started back in February. It took me awhile for me to get to it but I got to searching for a fix. and came across this community support. I read yours and I uninstalled the Dell Support Assist Agent and it seemed to take care of the problem.
Thanks a heap. Uninstalling the"SupportAssist" & the "SupportAssist Agent". I uninstalled the "SupportAssist Agent before I read I didn't have to. Do I need the "SupportAssist Agent?
It's the "Support Assist Agent" that causes the problems of 'buzz and skipping" on videos and audio. You can reinstall the Support Assist function when you REQUIRE "Support" from Dell.