September security update KB4515384 for Windows 10 Version 1903 caused many issues including Start Menu and desktop search issues. But later Microsoft acknowledged “Audio issue” caused by the KB4515384 update on the update history page.
Microsoft has received reports that audio in certain games is quieter or different than expected after installing this update. At the request of some of our audio partners, we implemented a compatibility change that enabled certain games to query support and render multi-channel audio. Due to customer feedback, we are reverting this change as some games and some devices are not rendering multi-channel audio as expected. This may result in games sounding different than customers are used to and may have missing channels.
Now, Microsoft has promptly pushed a new update KB4516421 fixing the audio issue caused by the September patch.
This non-security update includes quality improvements. Key changes include:
Addresses an issue in which some customers may be unable to use USB Audio 2.0 multi-channel microphones in Voice Recorder and similar apps.
This update is not available for manual download and installation and you need to check in Windows update to get the update.