Follow these simple steps to enable/disable Voice feature:
Open app side menu by swiping from the left side of the screen
Tap on settings
Swipe down until you see Voice Notification option
Tap on it
Tap on first option (Turn on/off voice notification in application) to enable / disable this option
When you enable voice notification you can choose interval type by tapping on it and choosing Time based or Distance based
You can choose interval by tapping on Interval and then choose on how many minutes or km/mi (depends on what you choosed for interval type) voice will be triggered
Also you can adjust Speak option by choosing what information app will speak