https://www.bleepingcomputer.com/news/microsoft/windows-10-1903-kb4515384-update-affects-audio-quality-in-games/

The KB4515384 Cumulative Update for Windows 10, version 1903 is causing audio quality downgrade issues in multiple games according to numerous user reports.

For some, the issue is noticeable in games such as Overwatch, Apex Legends, WoW Classic, and PlayerUnknown's Battlegrounds, while for others in all games the sound is very low volume and it seems to be muffled.