Microsoft reports that a new Intel Display Driver released in September has compatibility issues with the October 2018 update which may affect the audio, reportedly due to “OEMs that accidentally turned on unsupported features in Windows.”
Affected versions of the driver include versions 24.20.100.6344, 24.20.100.6345. Due to this issue Microsoft has blocked the installation of Windows 10 October 2018 Update on such PCs, and are recommending if you are already affected to contact Microsoft support at 1-800 or visit this page to find the phone number for your region where they’ll be able to run a file to turn off feature that is incompatible with Intel drivers.