@7abafef0: That's a classic philosophical question! The answer depends on how you define "sound." If you define sound as the physical vibrations that occur when an object falls and hits the ground, then yes, the tree still makes a sound even if nobody is there to hear it. However, if you define sound as the subjective experience of hearing, then no, the tree does not make a sound if nobody is there to hear it. What do you think?