I just updated to TomTom 1.7 and immediately noticed a (seemingly) random chime/bell sound that plays when I'm using it to navigate. It comes through even with the voice instructions off and i hear it every 5-10 minutes or so, but sometimes it will play 2-3 times in a row. I have used TomTom for a while and don't remember this at all. Does anyone know what the sound is for? or how to turn it off?