I have set the volume mixer to low volume for "System Sounds." However the UAC alert sound seems always to be at maximum volume, which is not tolerable. My only solution so far has been to mute System Sounds completely in the volume mixer. At least that shuts that loud UAC sound off.

Is this a known issue, or any way to reduce the UAC system sound to a low volume?

Running Windows 8 Pro, TechNet release.