Now pure physics will tell you that if there was no one there to hear it that no it doesn't make a sound, because sound is something the nerves in the ear and the brain creates from vibrations in the air, so if there was ear and brain near by to sense those vibrations there was no sound. And once again science misses the point entirely, though I think the scientist that came up with that explanation was just being a smart ass.
The philosopher that first came up with the question, first apparently worded it a lot longer because wikipedia (http://en.wikipedia.org/wiki/If_a_tree_falls_in_a_forest) even paraphrased it instead of giving the full thing, and second asked did it actually fall, not did it make a sound, and that I feel brings up interesting questions about the nature of reality.
If I observe a room with a single object on a pedestal, lets say a flower pot, and then leave the room, and no one else was in the room, does that flower pot still exist on that pedestal? If you were to go into that room and look for it would you see the same flower pot on a the same pedestal? Would it still be in the same room, in the same spot, or would your brain interpret the sensations it gets from the room differently and see a different flower pot on a different pedestal?
Let's say we get into a debate about what we perceived in the room and the placement and color of the flower pot, so we which go back separately and together to observe the room, and each time come away with the opinion that we are right and the other person say the room wrongly? Is it not possible that the two of us standing in the same room could see the same room differently?