The behavior is:
volume up and volume down result in the OSD pop-up being displayed and the volume going up and down. Mute does not result in any OSD nor the volume icon in the upper panel showing mute, but sound is muted.
The behavior is:
volume up and volume down result in the OSD pop-up being displayed and the volume going up and down. Mute does not result in any OSD nor the volume icon in the upper panel showing mute, but sound is muted.