On my phone, the sound in Navigator is somehow linked to the sound control in Music Player. If I ever lose sound when I want it in Navigator (after a bluetooth call in the car hangs up, for example(why, I do not know)), i open Music Player, find its volume on mute, switch it back on, exit Music Player, go back to Navigator and find that Navigator has sound again. Other apps on my phone have their sound linked to Music Player as well--the audio on Mobile Metronome can be switched on/off the same way. It's a toggle switch. To turn sound off in Navigator, switch Music Player to mute. No need to keep Music Player app open. Too bad if you are listening to music via Music Player. Guess I don't have all the answers.