Question: I've always wondered if Mark, just before his final broadcast, told his parents the whole truth. It would seem that way because Mark tells his girlfriend his mom let him use the Jeep ("She kinda loaned it to me"). Also, his Dad was at the gathering in the school's athletic field, but there is no shot of him acting surprised or horrified when Mark pulls in to where the crowd is and gets arrested. So the question is: did Mark fess up to his parents? Or is it irrelevant/left for us to wonder?
Question: How come Mark's parents couldn't hear him while he was broadcasting as Hard Harry in their basement? Wouldn't they hear their son talking?
Answer: The first time I watched the movie, I kept thinking that Mark's parents were going to hear him and catch "Harry" in the act. When the girl was with Mark, Mark's parents pounded on the outside door; when Mark opened the door, his parents said they thought they heard him talking to someone. So, from outside the garage door, someone might be able to hear muffled voices but not the actual words. Why his parents cannot hear him in the basement when they are indoors lies in the props/scenery plus some inference. The numerous objects in the room (tapes, CDs, albums, guitar, drums, bongo drums, recording instruments, amps, etc.) indicate that Mark is into music - loud music - and electronics. He apparently was given garage/utility storage space to turn into essentially a studio for himself and a place to play his drums and music without disturbing his parents. The space has been sound-proofed - thick concrete walls, insulation, and cloth wall hangings to deaden the sound.
Chosen answer: Well, with no actual scene where he confesses, it's left up to us to wonder. Personally, I find it unlikely that he'd actually admit the whole thing to his parents, but they're not stupid and already had their suspicions, so the lack of any great surprise on his father's part isn't unreasonable. You also have to remember that Mark's voice changer had already broken before they drove down to the crowd - his father would have easily recognised his voice before his actual arrival, giving him a certain amount of time to get through the initial shock.
Tailkinker ★