I see a few reports of this today and yesterday, so this may be an emerging problem in Windows 11.
Open the Settings App, go to System Troubleshoot - Other Troubleshooters.
Run the Audio Troubleshooter from there, to see if that can find and solve the problem.
If that does not resolve the problem, go to the support page for your PC on the manufacturers website to download and re-install the version of HD Audio drivers and Graphics drivers they provide.