We use the same channels as your music apps to play our voice navigations. Some Bluetooth Headsets are not set up to play music however. The headset needs to support this, so needs to be for example A2DP compatible (Android). Usually a simple Google search will help you (i.e. "play music with name of your headset"), to find a useful answer.
Please also note: you need to have started a navigation to be able to increase the volume of the navigation announcements. If you increase the volume before the Tour has started, this will have no effect on our announcements.
You can find on the switch to activate your announcements in Android under the loudspeaker icon at the bottom of the map of your Tour and on iOS under the three dots icon at the bottom of the map.