Windows 10 1903 KB4515384 update was released last Tuesday. Microsoft acknowledged that a change was made that would cause games to sound different or have low volume. This problem has been reported for games such as Overwatch, Apex Legends, WoW Classic, and PlayerUnknown’s Battlegrounds (PUBG) Microsoft plans on reverting the change in the next cumulative update being released at the end of September. Until then, Microsoft has provided the following temporary workaround that can be used in certain games to make them sound normal again.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-releases-workaround-for-windows-10-audio-issues-in-games/