I love stuff like this and if I weren't so lazy I'd have made a great social scientist. There's a scientific explanation for what are called aural illusions, but it boils down to people hear what they want and expect to hear.
There's another illusion where they clip a small part of a speech, and when they play that clip over and over it sounds like she's singing. This phenomenon is why I can't remember a single thing from my algebra classes....except how to sing the quadratic formula to the tune of Pop Goes the Weasel.