After upgrading my laptop from Windows 7 to 10, video sound both native and streaming became distorted. I tried uninstalling and reinstalling the audio driver to no avail. I then noticed that I was encountering the same problem whether I played audio through speakers plugged into the headphone jack or through the HDMI-connected TV.
I have also disabled all background apps in case they were somehow interfering, but it made no difference. Recently I discovered that the problem completely disappears if I use a pair of headphones.
I don't know how to describe the distortion other than to say it's like an electronic buzz, so I recorded it with my crappy mp3 player mic and uploaded it to Vocaroo (capturing system sound didn't record the distortion for some reason).

Here is an mp3 played with WMP through the TV:
Vocaroo | Voice message
You can hear the distortion at :06, :15, :18, and others. The worst one is at :32.

I've tried everything I can think of. Does anyone have any suggestions?