[kbfc]

I think our disagreement is due to the unclear definition of 'sound.' I'm taking it as just an example of 'some unexperienced event.' That said, I agree with your analysis of Hume for positive statements, but not for negative ones, such as "the tree made NO sound." I don't find Hume's philosophy to include any provisions that would explicitly deny the possibility of something unexperienced (if we can even narrow down what that means).

Just because he cannot say for a fact that it made a sound, that doesn't mean he can say for a fact that it did not.