hmmm, probably. i'm likly mis-using "existential" i dont mean it as the "-ism". the sound, the wave, exists regardless of whether it is perceived or not. the original tree falling question was asked in a time before we know what sound was or had proxy devices to record such events...
all well argued, but you're playing around with technical semantics. the mechanical wave is created whether something is able to perceive that wave or not. "sound" defines the perception, not the physics. the tree falling still makes the waves, and that isnt changed by the presence of a human...