 This seems to imply that the question is posed not from a philosophical viewpoint, but from a purely scientific one.Note that, from a scientific perspective, possible listeners would include animals (see earlier phrasing, mentioned below).The magazine "Scientific American" corroborated the technical aspect of this question, while leaving out the philosophic side, a year later when they asked the question slightly reworded, "If a tree were to fall on an uninhabited island, would there be any sound?"