put a sound recording device next to it and it will but no one is there to hear it? That includes a person putting a recording device there. It is impossible to tell if it will make a sound, because we only know sound happens when people are listening, or something is observing it. My feelings on the whole tree thing are upon falling it would cause vibrations therefore making sound waves. However, sound is just the sensation when our brain converts soundwavs into what we call sound. Therefore, if no one was there to hear it, there would be no brain to convert the sound waves to sound, therefore there's no sound made. ^^That's probably a bit confusing. At the bottom of the wikipedia page I found the link to the .999...=1 more interesting.