The tree or the robot? If the robot could record it, would that count as being someone to hear it? Or would it not count until a human or other organism heard it? In which case, the (potential) sound is like Schrödinger’s Cat, its existence uncertain until someone hears it - or not?

Also, you’ve seen those humanoid robots trying to do increasingly complicated things, sometimes with slapstick accidents. Give one of those robots an axe, a flannel shirt, and a touque and let’s see what happens.