[kbfc]

Well, this question is pretty silly. I don't agree that Hume would say there was no sound. He wouldn't say anything definite like that. For Berkeley, the question is sorta nonsensical. Since, for him, basically everything exists in the mind as provided by God, the notion of an event that doesn't get experienced is contradictory. I guess the 'proof' you'd want against his position could be easily summed up as, "Berkeley is full of [censored] on everything, so why should this be any different?"