I learned this in my Physics class. There are three basic elements for transmission and reception of sound that must be present before a sound can be produced. They are (1) the source (or transmitter), (2) a medium for carrying the sound (air, water, metal, etc.), and (3) the detector (or receiver). The argument would be that if there is no receiver, there may be no sound!
Second, sound is a subjective interaction with matter. All that sound is, is vibrations through a medium, without humans to perceive it, those vibrations that we call sound, when the tree fell, would make vibrations, but “sound” as we know it, couldn’t exist, since no conscious being was there to interpret those vibrations.
A Simpler Answer: For example, if a deaf person was in the woods and a tree fell, would it make a sound? No, because their auditory system would not pick up the vibrations that make sound. They may feel the lower vibrations in their body, but not the sound.
There. Hope that gave you some brain food. Doesn’t it make you wonder why you took the phenomenon of sound for granted?