Hi
When I updated to Windows 8.1 on my desktop, I had problems with the sound being distorted.
I found a lot of other people having sound issues as well.
I finally gave up and went back to Windows 8.
In my case I think the problem is with the driver upgrade, when updating Windows.
Since Windows 9 beta is so close I haven't tried again, but I suspect that if you can find the old drivers that you were using in Windows before updating and get the tablet to use them instead of the new ones it may fix your problems.
Mike