By tapping on Main menu → Settings → Bluetooth you can set the output of the voice instructions and notifications. Select Device default or Play over phone speaker
If you select Device default, Sygic will play sounds, instructions, and alerts from an externally connected speaker (for example, if you’re connected via Bluetooth to your car speakers).
Play over Bluetooth (HFP) – Play the voice instructions and notifications from another output device, e.g. car radio or handsfree device.