Well, speaking as a parent whose kids had horrible timing (Jimmy interruptus), we never got caught. Since Clark has Superhearing, I doubt he would get caught either. I do remember a story where the oldest boy found out he had superpowers by looking inadvertently through his bedroom wall into his parent's bedroom. Unfortunantly, Clark was in The Suit, having just returned from some superduties. So what the son thought he saw was his mother being unfaithfull. It was well done and quite humorous.
I'll see if I can find a link.
Artemis
Found it:
http://www.lcfanfic.com/stories/2000/dawnofdi.txt
