Not sure sonar has anything to do with this, but the timing is suspiciously coincidental:  have never had audio problems before, but after installing Dorchester I now get a hum from the headphones; goes higher or lower depending on windows open.  
 
Something (Dorchester?) used "WudfCoInstaller" and created a log file, including many of these error messages:  "AudMig: No audio endpoint migration settings found"  and "removing existing settings in preparation for setting new ones".   

Some Windows thing. Most references I find to it refer to upgrading from Win7 to Win8. This might be a good one to take direct to Cakewalk Tech Support. I' not finding any previous references on the forum. Here's an MSDN link:
 
https://msdn.microsoft.com/en-us/library/windows/hardware/ff561384%28v=vs.85%29.aspx
 
If all else fails, maybe try backing out your Dorchester update (if you used CCC) to start with.

I'm leaning toward coincidence.   Tried rolling back the update, still had the noise.   Messed with cables and reseated audio and video and it seems much less, though still there.   Thanks for the help.