also have an air safety expert. if these pings are not coming from flight 370, what else could explain them? >> well, really it's anyone's guess and we will probably never know. there are a lot of things in the ocean that make a lot of nois. this is a very artificial sounding noise so it boggles the imagination that something natural could create it. but we just don't know, really what could cause a false positive. we do know that there have been numerous false positives so far. it is very much in up in the air. >> the science tries to avoid this, the 37.5 kilohertz is a frequency not heard in nature? >> user error might be the answer. as someone pointed out earlier on cnn, there is a lot of