Mercedes-Benz S-Class Owner's Manual page 335

Switching the sound on/off
On the multifunction steering wheel
On the multimedia system
To mute: press volume control 1.
#
The 8 symbol appears in the status line
of the media display.
You will also hear traffic announcements and
navigation announcements even when the
sound is muted.
Multimedia system 333
To switch on: change the media source or
#
turn volume control 1.
Adjusting the volume
On the multifunction steering wheel