Switching the mute function on/off
On the steering wheel (MBUX multimedia system)
On the control panel of the central display (MBUX multimedia system)
To switch off:
press button
. The current audio source is muted.
The 
symbol appears in the status line of the central display.
If you are listening to a radio station, for example, and switch off the sound then all media sources will be muted.
Traffic and navigation announcements can still be heard in this case. The MBUX Voice Assistant and telephony are also not affected.
To switch on:
press button again. or
Set the volume.
or
The media source changes.