Phantom Audio in a Video

We imported a quicktime movie that has no audio into Flash, and now, mysteriously, it has audio. I didn’t realize what had happened at first because it’s video of a rocket launching and the static sounds like the roar of a rocket. I just assumed it was the sound from the original file, but as I have learned now there was none. So where did the sound come from?

Has anyone heard of a problem like this before?