Snooper Truckmate S6400 Voice Guidance

Hi all! Does anyone know if it’s possible to turn off the voice control on a Snooper Truckmate S6400?

My boss has let me borrow his to replace my car TomTom and I’ve always used that with the voice turned off. I know I can just turn the audio off completely however I’d like it to play the warnings sounds for speed cameras etc. If it’s possible, it’s beyond me!

Any ideas?

Jack