The Gravitational Waves We're Looking for Have a Very Specific Signature

It will be a much more difficult thing to demonstrate we've seen, than the gravitational waves we've see so far. It's easier to see things that are like individual cataclysmic events. But as you say, if we're just looking for a hiss, it's much harder to know if that hiss is coming from gravitational waves or from wiggles in your detector. We do these numerical relativity calculations that predict the signature, the finger print, of these gravitational waves. They're very short lived, and they look different from everything else.