You can change the voice guidance voice in Waze to several different languages and accents. If Google Maps ever had this option, they dropped it, for now at least. BTW Google now owns the Waze app. Don't confuse voice navigation voice with voice search settings. They are separate functions. read more
Try a different voice. I use Ivona, and it works currently. But sometimes when Google updates Maps it gets screwed up and reverts to the default voice. Sometimes it's just a matter of resetting it and rebooting. Other times it requires uninstalling Ivona, and reinstalling it, and occasionally it won't change until Google updates Maps again. read more