While I was thrilled to be able to navigate the S4 using my voice almost the entire time (except for volume tweaks and hanging up), I was only moderately satisfied with the audio quality. Callers commented on how faint or far away I sounded, and they heard a low level of muffling overall. When I had my windows rolled down, my test buddies picked up the sounds of other cars whizzing by, but this traffic noise did not bother them. Voices emanating through the S4's speaker sounded reasonably clear to me.

The S4 is a good candidate if you want to interact with the device using your voice most of the time. That way, you can keep your hands on the wheel and your eyes on the road.