neowin[.]net/news/microsoft-shares-workarounds-for-broken-audio-on-windows-10-after-kb5015878/
docs[.]microsoft.com/en-us/windows/release-health/status-windows-10-21h2#2887msgdesc
This problem seems to have flown under the radar, & being hearing impaired, I so rarely use audio nowadays I had to spend a bit of time making sure this PC wasn't effected.
KB5015878 itself was the 2nd, optional Win10 update for July, 2022, which included: "... numerous bug fixes and enhancements, including gaming and Windows Autopilot fixes and a new Focus Assist feature."
bleepingcomputer[.]com/news/microsoft/windows-10-kb5015878-update-released-with-gaming-fixes/
It looks like it effects systems that have audio enhancements turned off, or systems with drivers installed that have problems with Windows audio enhancements. Right-click the audio Taskbar icon, select Open sound settings, click Sound Control Panel, select the playback option, e.g., speakers, click properties, & finally click the Advanced tab to find the checkbox for Enable audio enhancements. Microsoft used Known issue rollback to stop the audio-related updates from applying in the future, but if the update has already been installed it's too late.
If only certain apps are impacted, you can try the following to mitigate the issue:Verify that the audio devices set within those apps are the expected devices. Audio endpoints might be reinitialized after KB5015878 is installed and some apps might set the audio devices for microphone and speakers to default.
If the device settings within the app are as expected, the apps might be caching the Windows Multimedia Device (MMDevice) ID. Caching the MMDevice ID is not recommended and might require reinstallation of the affected app or contacting support for the developer of the app for how to resolve the issue when audio endpoints are reinitialized and have new MMDevice IDs.If you have already installed the update and are experiencing issues with audio on all apps, you can try the following to mitigate the issue:
The Windows audio or sound troubleshooter might be able to resolve the issue for you. You can launch the troubleshooter from Fix sound or audio problems in Windows by selecting the Open Get Help button in the article. The Get Help dialog window should open, and you will need to select yes to open the troubleshooter.
If your device's audio is still not working as expected, follow the instructions in Disable Audio Enhancements. Note: The article uses the microphone as an example, but you will need to do the steps for any affected audio device.