So, I recently started using Ubuntu (aka within 6 months) and this is a brand new problem that I have never dealt with before. At first I was having problems playing sound from .mkv and .mp4 files (I was using VLC player). Files that used to run fine, now play without any sound at all. Then sound at the top range of the volume started sounding distorted. Now sound at all ranges sounds distorted. Although system sounds seem to be fine. I thought it might be a hardware problem, but when I plug in headphones I get the same distortion.