Question

when we wave the trees will fall down because of​

Answer 1

Answer :

Sound is something within human experience. Outside of this it's just air (or whatever other medium) vibrating. If someone is there to hear it, it makes a sound, if not, it causes rapid movement of particles.

Seth, Edinburgh, Scotland

I've always thought the point of this question was: if there's no way to establish whether there was a sound, then it ultimately doesn't matter. In fact, you could say that the definition of a sound is its detection, rather than the physical phenomenon. Of course, once we develop an instrument that can detect vibrations we couldn't otherwise hear, a previously non-existent sound comes into being.