If a Tree...

If a tree falls in the forest, and there's no one around to hear it, does it make a sound?

A falling tree creates vibrations in the air (as well as some damage on what it falls on). Vibrations in the carrier medium are not sound. Sound is when someone perceives those vibrations and therefore hears sound.

I hope this makes it perfectly clear and answers the question once and for all. Now on to the chicken or the egg experiment.