Navigation volume control sets wrong 'sound type'
I tried to use navigation and couldn't hear a tts voice.
Using my nexus 4 settings for the cell phone, I was able to hear tts voice outside of Locus.
It turned out that Locus settings for navigation were all correct, but one was misleading/not working as expected.
The problem is on the navigation panel which has 'Track', 'Itinerary', 'Recalculate', 'Nearest point', checkbox for 'Mute sounds navigation', and 'Volume' slider.
If the slider is set to 100%, but the cell phone system setting has 'notification' volume set to 0%, then Locus will not speak out loud. From this, it appears that Locus uses 'notification' channel to speak and probably otherwise make sounds. That is one problem.
The other is that when I use the slider control in Locus to lower the volume, it operates on the 'Music, video, games, & other media' volume level of the cell phone, not the 'notification' volume.