Windows Update 1809 (October update) was problematic for many, so much that Microsoft had to halt it for a while. Of the many issues reported by users, one was:
Audio Lost After Windows 10 October 2018 Update
The primary cause behind the issue is that the Windows Update 1809 messed up with the system files of the system it was installed in and this in turn affected the audio drivers.
Microsoft has released another update KB4468550 to help resolve the issue with audio, however, in case the system files have been messed up with already, they would have to be fixed.
Other than updating Windows, the following solutions would be helpful:
1] Re-install the audio drivers (if possible)
2] SFC scan
3] Roll-back to the previous build of Windows
4] System Restore
Solution 1] Re-install the audio drivers (if possible)
The audio drivers could be reinstalled as follows:
1] Press Win + R to open the Run window and type the command devmgmt.msc. Press Enter to open the Device Manager.
2] Expand the list of Audio inputs and outputs.
3] Right-click and choose Update Driver Software for each of the audio devices.
4] You might also consider uninstalling the drivers (right-click >> Uninstall device) and restarting the system. The drivers would get reinstalled automatically.
However, if the driver is broken or the concerned file is missing, it might not be as easy a task.
Solution 2] SFC scan
In case this issue is caused by missing files in the system, an SFC scan could be helpful. Here’s the procedure for an SFC scan.
Solution 3] Roll-back to the previous build of Windows
Since Windows update 1809 is known to be troublesome, it would be a good idea to roll-back to the previous build till a stable version is launched and users have confirmed that it is issue-less.
1] Keeping the SHIFT button pressed, click on the Start >> Power >> Restart.
2] The system would restart in Advanced options.
3] Choose Troubleshoot >> Advanced mode.
4] Select Go back to previous version.
Solution 4] System Restore
Restoring the system might help bring the lost files back. Here’s the procedure for the same:
1] Go to Control Panel >> Recovery >> Open System Restore.
2] Run through the System Restore process. It would ask you to select the restore point and then to confirm the restore point.
3] Restart the system once done and check if it helps with the issue.