Yea, what they said... You can mute a phone call during a conversation but as far as any of the other features (XM, radio, navigation, etc.) just use the knob on the infotainment center or the buttons on the steering wheel to turn the volume down/up.Turn the knob on the front of infotainment or use the volume control on steering wheel pressing on volume- button until sound level is achieved.
but you cannot mute the Nav voice entirely. I have been frustrated with this for days. It doesnt allow you to fully mute the Nav voice, plus it will interrup the Stereo audio everytime the Nav command screen changes.