Yes they can sense vibrations easily, but I think saying that they "recognize your voice" may be anthropomorphizing them a bit too much. I'm not quite sure why but people always seem to be trigger happy to proclaim that their pets have this 6th sense that allows them to connect with their owners somehow. Did you ever think that perhaps being that Ball Pythons are very shy that the high-freqency vibrations being put off by your voice scared the snake into being still? Its certainly not out of the question.