I have a question about this whole "the faster your going the faster time passes around you" thing?

The guy going fast hears himself the same. Time is slowed, but he can't realize time has slowed without looking to the outside world. As the waves from the walkie talkie exit the region where time has slowed, they'll be the same frequency, so it's the same voice. It's just time has now become faster again, back to what we consider normal. He doesn't have a high pitched voice just because he's going fast :P