Some Sferics sound amazing like a human voice speaking but is just muffled enough that you can't quite make out what he's saying. Other times it sounds like frogs on a swamp. Some pulsars sound like someone stomping around in heavy boots in a large resonant empty room. I have a recording from space that sounds incredibly like Merzbow where if I hadn't gotten it from a University website who record and post their own sferic and outer space recordings would have been convinced that it was Merzbow. So while I can't say these defintely weren't faked (they're on youtube after all), it would be remarkable for me to have managed to pick at random nothing but faked recordings.