Recently bought a 13 plate 1.8 Venture Edition and unable to find a volume control for voice instructions. It’s at Tom Tom unit with a mic icon on the left side which when pressed moves to top right with a coloured quadrant which does nothing. There is no section in the hand book and have looked at the various 160 page instructions available on line none of which are similar to mine.
I have a mark 4,and someone i knew with a mark 3 had the same sort of query,it turned out it was just the same to alter the volume regards sat nav as on the mark 4,the volume control that alters the volume regards the radio,when the sat nav is actually giving an instruction at that moment and only at the moment the sat nav is giving instructions ,the radio volume control knob alters the sat nav volume,it does work very well but you have to be quick to catch it at right moment.
I can’t confirm if this is correct but rather than waiting for an instruction to occur and then having to jump to the volume control there is usually somewhere on a tomtom screen to touch and repeat the last instruction. This may also bring up an on-screen volume slider.
Page 28 - Touch the status bar to repeat the last voice guidance message.
Page 43 - Increase the audio volume during voice guidance by pressing the + volume button. Decrease the audio volume during voice guidance by pressing the + volume button.