monitor the ocean below. the search teams say their greatest asset is the human eye. to avoid fatigue, crew members are switched out from the 11-hour flights every day in the search zone they scan the water in 30-minute shifts to maintain con concentration. have you spotted anything on this ship? no, no, unfortunately not. we re just going to carry on though. so, yeah, we will be in half an hour. see how it goes. reporter: even after so many weary hours of searching, fatigue has yet to dampen hopes of finding flight 370. matthew chance, cnn, over the indian ocean. so right now 12 planes, 14 ships involved in in sunday s search. they may face rough weather, possible isolated showers. time is running out. battery powered signals from the black boxes may soon go silent. mary schiavo, first to you. how would fatigue play into this
aeroplane. and that would obviously narrow it down dramatically. but even if it doesn t pick up anything, it is sweeping the floor, possibly eliminating the areas where we don t need to put the bluefin-21 down two. michael kay, you re giving him the thumbs up here. why? geoffrey is spot on. three days in the context of a search that could last for years, i don t think we are wasting time. what we re doing is, angus houston is making absolutely unyou ve kabquiequivocal 100% s all the possibilities. as soon as you put it in that s it, we re in the for the long haul and it could take years. why is there only one bluefin side scanning sonar? why can t we use five or six of these to search faster? i think that s a david gallo question. good question. we had three similar vehicles.
search, of course, there s the ocean surface, so you ve got all the garbage we throw in our oceans which definitely throws an obstacles for that search, for that visual search at the surface. and down below that surface there s something called noise pollution. and manmade noise pollution is certainly a factor in all of this, as well as just the natural ambient noises that nature makes. manmade noise like what? low and mid-frequency sonar, for example, that have been known to enter fointerfere with migrations. beyond that it just creates a huge soup of noise. thus, the issue with putting the sonar in there now because you get that frequency. let s find out a lot more about this, about sounds with this precious ping among all that random noise requires huge amounts of skill. audio experts looks at gazillion of sounds just to find one black box ping. we have someone here to show us the use in the search for pings.
reporter: 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 noiszs competing with the sound of the pinger like sea life. one dolphin species sounds like a black box pinger. and this the sound of rain under water. let me get away from the loudest part of the boat so i can show you one of the biggest obstacles that searchers in the v. in the open sea, just ship noise, even here listen to how loud it is. they re at a minimum 15,000 ships on the world s oceans on any given day. creating even more obstacles in a search that s already
investigating civil aviation and military authorities to determine why opportunities to identify that plane, to track that plane were missed in those very chaotic hours after the plane vanished. note, we here at cnn have been reporting the malaysian air force sent search aircraft on march 8th to the south china sea and the strait of malacca according to sources. but apparently the military did not tell sivill civilian author until later. it s still under contention. don? joe johnson, kuala lumpur. praying for a sign, staring at the motion, i should say, praying for a sign of flight 370. the search for the missing plane will take a toll on anyone. straight ahead, could fatigue make it even harder to find the airliner? i have low testosterone. there, i said it.