researchers show us the challenges search crews face as they try to hear the ping from flight 370's data recorder. >> so this is a hydrophone. >> we drop an underwater microphone, a hydrophone, off the back of the boat as it moves farther away from a pinger that's already been submerged. and even less than 100 yards away, the ping starts to fade. distance isn't the only problem out in the indian ocean. there are other noises competing with the sound of the pinger, like sea life. one dolphin species sounds like a black box pinger and this is the sound of rain underwater. let me get away from the loudest part of the boat, so i can show you one of the biggest obstacles that searchers have in the open sea. just ship noise. even here, listen to how loud it