If a tree fell down...

Yes, because noise can be defined as a vibration of air, whether it is perceived by auditory senses or not.

We roughly defined noise -sound- as those vibration that we can hear. So if there were never ears, at all, then it wouldn't have been called a noise, and you couldn't ask this question. But there are, and we did define the type of vibrations caused by a falling tree as noise, so it's still noise when nobody is around.

Now, I did assume there that this particular tree will make a noise when it falls, based on the fact that all trees we observed so far while falling, made a noise. The old induction problem. We can't be entirely sure that all trees are noisy when they fall, just because we've only seen trees that produce noise when they fall. There is a theoretical chance that this particular tree will produce a rainbow instead, or an identical copy of the mona lisa. But for practical reasons, we usually ignore those chances, which serves us quite well in predicting what will come out of a certain event. Especially in simple systems like trees falling. (Though, to predict what the exact noise will be, or how the tree will land are again impossible to predict with accuracy, even with the most advanced computers, because of chaos effects.)

Last thing: Are animals and bugs also not around? They can sense noise. But many of them might not be able to understand it came from a falling tree, because they don't understand causality like we do. Also, they won't remember. Are things or events that nobody remembers or understands, "things" or "events" at all?

Yes, but that would make it a moot question, wouldn't it? If something that probably doesn't exist does something, does it make a sound? Indeed, probably not. But since the existence of the tree is implied in the question, I think we must acknowledge its theoretical existence at least, including its falling. Or we could ask no hypothetical questions at all.


I assumed we shared enough culture to agree on the meaning of sound, being that which is audible. If you wish to talk about a different "sound", I think it should be defined, and we can use that definition for the length of this discussion.. Or indeed, think of another word for it, when your definition is so far off the commonly used definition of "sound", that it would be confusing to use the same word.

Yes, there's two ways to get there. The one is Hume's, in which you doubt the principle of causality. Just because X has always happened when Y, that doesn't mean it always will.

The other is the solipsistic view. That is: anything outside our field doesn't happen at all. In fact, I am the only person on earth who is real, and I am imagining all of you as I go. If I can see a tree fall in the far distance, but I am out of the range of the sound, it did not in fact make a sound.

Which do you prefer?


Yes, I suppose it is relevant. But I think they would call it sound if it was still a very different sensation than any other pressures they could feel. They would learn that we call these specific pressures sound, and then we are talking about the same thing again when we mention sound. Which is how communication works, of course: by sharing similar words for similar concepts.

If they wouldn't be able to discern sound from, say, a spinning fan that causes air ripples, then we'd find it very hard to talk about the sound of a falling tree. But I think all of this has more to do with communication about the sound of a falling tree, rather than the fundamental question of there being sound at all. So perhaps I'm getting too far OT.