Well, I understand your point but it is not intuitive when compared to the big competitor google maps. That's why it took me so long to realise that my phone was in silent mode. If you insist on being silent, when the phone is in silent mode, then I suggest to disable the specific items so that it is clear to the user why he can not hear any noise.
I have my phone in silent mode for 90% of the time and only want some selected apps to be able make "noise".
Peter