If you do a Site search I'm pretty sure you'll find a thread on this. Seems to me it was a mobile setting somewhere (as in, for when you're in your car)
You need to look a couple different things in the phone's settings.
First, go to Settings -> Accessibility. Make sure that TalkBack is turned off. If for some reason you want it on for something, tap the Settings bar at the bottom. From there, you can change several of the TalkBack features, including when for it to talk and not to talk according to the volume.
Second, go to Settings -> Language and input ->Text-to-speech output. Make sure that "Driving mode" is turned off.