The "Manage sound devices" panel should show a list of "Output devices" and a list of "Input devices." Click on one to disclose a Test button and a Disable button. You should see your headphones show up twice in the "Output devices" menu. Testing one of them will result in a clean sound, the other will result in shit sound (due to SelfVoice). Press "Disable" on the one with shit sound.

Then do it again next time Windows Update runs and clears your user settings, and again, and again, because apparently clearing settings to default is something that Windows Update does now (I've seen it in other places too).