then there s that emergency beacon itself. where it is the batteries won t be good for much longer. today is day 31 since malaysia airlines flight 370 vanished. in the indian ocean right now a frantic search is under way to track down three mysterious pulse signals. two of them apparently matching the same frequency of a black box pinger. cnn aviation analyst mary schiavo, cnn aviation analyst les abend, paul ginsberg, forensic audio expert, hopefully you ll become an analyst here on cnn. i would love that. mccallum, cnn analyst and ocean search specialist. i m going to play examples of the sounds they re now listening for. the first is called a chirp pulse. listen. [ chirp pulse ] the other is called a pure pulse. [ pulsing ] all right? so those are the two things. those were played those were