listening to cockpit voice recordings, it would be the same thing. but they're on different channels. >> correct. there is a lot more information recorded on the cockpit voice recorder than can be gleaned from listening to the single challenge received radio signal to the tower. >> yeah. do we have, producers, if we can, the sound of the pings and the chirp and the tone that paul ginsburg supplied for us earlier? i think our viewers would like to hear that. because we're trying to figure out, we have been trying to figure out throughout this whole thing if in fact what the chinese ships and the australian ships have picked up if it is in fact cockpit voice recordings or the black boxes that are presumably on the bottom of the ocean. and you're saying these aren't the exact sounds, but these are sounds that they would be looking for, similar sounds. first let's listen to the pulse tone. [ beeping ] >> that's the pure tone.