people are looking way too far into it...i actually think that this cant be answered based on science, its really an opinion question. are the things we believed perceived, or do they actually happen? We believe it will make a sound, because if we were there, it would. Why does it need to make sound? to let us know something is happening. if u think about it, because it would normally make a sound, it should still make that same sound. however, its like ...put in another way (i actually think that this is from the movie the Santa Clause or some shit)...if u've never seen a million dollars, how do u know it exists? U've seen enough money in ur lifetime to have seen say, 10,000 dollars, and know there are millionaires, but u've never actually seen a million dollars. what about a tree falling? u've probably seen them on tv, know that sound, have seen a FALLEN TREE in the woods, so u know it MUST have made a noise.
its not just a tree, like people have been giving examples, its anything...a rock falling off a cliff will still make a noise.