Christine asked:
If a tree falls in the forest when nobody is around, does it make a sound?
Answer by Peter Jones
Hello Christine,
There are a few answers to this question depending on what it is supposed to asking. Here are some of them.
A physicist would answer no, of course not. A pressure wave only becomes sound when consciousness works it magic and transduces it into a series of experiences. It is even questionable whether a falling tree makes a sound even when there is someone around, since the only evidence we have for sound is first-person reports.
A panpsychist might say yes, of course it does, because there is always someone around. Were there not, there could be no forest in the first place. They might also answer no, since the somebody who is around might not have ears.
A sceptic might say that the question is incoherent. It assumes the reality of the forest, an image on our retina, and thus also the reality of the pressure waves, an image on our eardrum, then questions whether there is a pressure wave when a tree falls that would have been heard as a sound had somebody been around to hear it. The answer is obviously yes. If we doubt that the sound is there, even in its potential as a pressure wave, then we might as well ask whether the forest is there when nobody is around, or whether our boyfriend is there when we’re not around.
A mystic might say, with the usual ambivalence, that it would all depend on what level of analysis we are working at. All the above answers would be correct, and there would be more.
If it is a question about logic, about what we can learn by simply working it out, then the unfalsifiability of solipsism on its own prevents us from reaching a firm conclusion. We can learn from the question, but we cannot answer it except by reference to a tautology. If the forest is there then so must be the pressure wave, and the sound may or may not be there depending on whether anybody is around.
My own view is that it is not a challenging question. Once we assume the existence of the forest we must assume the existence of pressure waves with the potential to be heard or not heard. Clearly if there is nobody there they will not be heard as sound. This is not a metaphysical problem but a muddled question.
For a more metaphysical question we would have to drop the assumptions and ask: Is anything at all there when nobody is around? Is anything there even when somebody is around? What is this power that we have to hear sounds? And who is it that is listening? And so on.
Ask a Philosopher 
And can nobody be somebody? Or am I just dreaming?