I can't take credit for the SOLUTION to the audio distortion problem in 15.5 and Windows 10 host. But, here is what someone else suggested, and it worked like a charm:
Open Windows Media Play, set it to Now Playing, and then minimize it. That's IT! If you don't believe me try playing some system sounds, like Windows log on or Windows Exit, etc.
I have no idea why this works but it DOES.
For your information, I do NOT have the problem on my Asus Z97-pro Tower, running VM 15.5 and Win 10 as the host.
I only have the problem on my Lenovo P50 laptop with the same versions. Go figure!
Note: I just discovered the fix is not a permanent one. If the distorted audio drives you as crazy as me, you'll have to start Windows Media Player in your virtual machine and set it to now playing and then minimize Each and Every Time you fire your XP or 7 virtual machine up!
Maybe someone can figure out a permanent fix??
Hope this helps!