 The radio chatter audio near the end of the film as Ben returns to  the beach is actually a recording of a Norfolk Southern train defect  detector. If one listens carefully you can even hear it state, "NS  (Norfolk Southern) detector milepost 79.8 one no defect." The actual  detector likely reported 79.8 track one but the word track would  spoil the illusion. It is interesting because these automatic  reports only transmit two or three miles to inform the train crew of  defects in their train. It is not likely they would be heard on a  remote island.