It is not odd to hear a strange noise in the sky - there could be any number of explanations or they could be hoaxes etc. I'm not going to waste my time going through them. What presumably interested a couple of sensible people on this thread was that this was, apparently, heard over the whole country very recently. Costa Rica has some 4.5 million inhabitants, presumably including politicians, scientists etc etc - from that we have one video (in an age where practically everything is captured on mobile phones) and a couple of sketchy news reports. All I want is some compelling evidence that something was heard. Even that one video seems to have gone now. Probably a CIA cover up though eh?