The Question:
If a tree falls in the forest, and no one can experience it, does it make a sound?
My most thoroughly reasonsed answer
I'm of two minds what this question is really asking.
My first answer is no, it does not make a sound. Sound is an experience. *However* it does produce compression waves in the air. My mind on this question is that it shows that there is a difference between the experience and the cause of the experience. It's a common mistake that many people make, and we have to rememeber that experiencial properties (color, odor, taste, sound) are all secondary qualities, which ride backseat to the primary properties (Mass, volume, charge, etc). This question is also asked in "What color is an orange in the dark".
On the other hand, the question could be asking the importance of an observer to an activity. Of course, then we can say-those of us who hold an Ultimate Observer-that there is always an observer, so yes the tree falls and it does make a sound. Without an ultimate observer, the answer would be yes or no, depending on your philosophy.