I never interpreted the question the way presented in the article. I always interpreted it as "Does something exist if it is unobserved?" and therefore never cared if the sound of a falling tree is heard by a human, recorded by a cassette recorder or recognized due to seeing a tiny movement of a light object caused by the pressure wave. This problem seems - at least to me - to be much more interesting than arguing about the (correct) definition of sound (to use in this context).