How to disable event sounds in Plasma 5?
In recent Plasma 5, search "Audio Volume" in the application launcher and, under 'Applications' tab, disable 'Notification Sounds'.
In some Plasma versions the above doesn't work, as I now see in Kubuntu 17.10. The Audio Volume tool looks different and notifications sounds is already muted.
To stop the volume scrolling sound etc in this case, I have unmuted, and moved the slider to zero, and muted again. Something is buggy here though, as the slider is in fact always stuck to zero, and only the mute/unmute button does the work.
In this case I have noticed that a different tool can be used: pavucontrol-qt
:
After using this, the bug mentioned (slider stuck to zero in "Audio Volume") disappeared.