The driver/software package on this laptop includes a Dolby Surround Virtualizer.
I've noticed while this was Win8 that if I had 2 things playing sound, one would be favored and would virtualize Surround Sound, making it much louder, and pretty quality sound. Any second, third, etc sources of sound would sound tinny, about half volume, and quieter.
I assume the Dolby virtualizer does this. With Windows 10 it would seem something is constantly taking that primary slot, because now everything gets that background, tinny sound. I can turn the Dolby thing completely off, on, virtualizer on and off, restart, etc etc, nothing fixes this. I'm guessing maybe Cortana is causing this? Whatever it is, some sort of tweak needs to be made to how this works on Windows 10.