Seen this pic?
From philosophy class, if I remember right, the tree making a sound thing has something to do with existentialism
. Can't remember much about it though since I slept through most of that class (still passed with a B!). I remember the most correct answer was no it does not because sound is how we interpret airwaves and without someone to interpret then it doesn't exist. It's like how you were saying that we make the universe around us.
I saw a commercial for a special on discovery channel about the universe and some of the new hypotheses and ideas about it. Something about our reality not being what we believe it is and how 3D is made up by our brains to make life easier. Interesting stuff.