Angus Benson-Blair

Firstly, apologies if I am being a muppet here. I have just got my new galaxy fitted with the 7'' touch screen dvd nav system. The question I have is to do with turning the stereo bit of the system off. So far it seems that if I want the climate control on and/or the sat nav on, then I have to have the radio/cd/aux on. Is there anyway to mute the system without having to revert to using the volume knob?