become much more difficult. >> reporter: the cockpit voice recorder stores at least two hours of audio and the data recorder contains at least 36 hours of instrument data, both crucial to understanding what happened. transmitters on the recorders send out a locating tone. but that only lasts for 30 days. malaysian officials say without the pings, they don't have the technology to find them on their own. >> looking and then before that becomes an issue then malaysian submarines don't have it. >> reporter: it may have sunk far from where the debris has drifted. the water can be 13,000 feet deep, ten times height of the empire state building. >> it becomes a situation of trying to hear a very tiny signal in a really complex background noise. and that's a hard problem no