Most the time, when a user’s sound is scratchy, it is because they are over driving the alsa sound driver. The solution typically is to go to YaST > Hardware > Sound > Other > Volume and move the volume controls UP there, and then close that, and go to one’s mixer, and move DOWN the controls for Master Volume and for PCM.
Yesterday I’m uninstalled my pulseaudio packages because scratchy sound. Now I can watch YouTube and vlc, listen to amarok at the same time and no corrupted sound. (Usually I’m not doing all 3 things at the same time - it was just a test :))