Maybe another way of putting it is, the waves exist but it is our perception of these ways that we call sound. Vibration waves that are 2 high frequency for us to hear would also exist but since we can't hear them we would not call them sound. But if the high frequency waves created some affect that we could perceive such as vibrating objects we might refer 2 the waves as high frequency waves as opposed to calling them sound. Is this close to your idea you are entertaining?

It seems to come down to mainly what is your definition of sound and what is your definition of hearing. Is this subjective? Can we have various Concepts of a definition for sound. Sometimes definitions or changed in dictionaries for various reasons. Recently it has been brought to my attention that the definition for the word fascism has been changed in dictionaries for political reasons. That can be an interesting discussion too. Perhaps I will post about that.

When I say no one around to hear, I intended the inclusion of animal life with auditory receptors. Vibrations and pressure waves exist regardless of ears to hear, but I entertain the idea that sound is an exclusive quality attributed to a biological entity that is capable of detecting the pressure waves.

If a man speaks in the woods, and no women are nearby to hear him, is he still wrong? Old PHC joke. It bore repeating.

Ultimately I would like to think that in any realistic circumstance, that any of the definitions I have read would all theoretically be a yes. So, say this theoretical tree falls and no human is present. Well wildlife, the obvious retort, I have also read the plant based biological life, which although isn't as easy of a sell still makes sense. Even still if there were to be no other plant life or perceivable wildlife, isn't there still some form of single celled living organisms, that would indeed react to the very vibrations in the air that makes up their atmosphere. To delve even deeper, wouldn't these sound waves effect the indistinguishable partials of matter in the immediate area, and who's to say exact ally how far that ripple effect would travel, changing the path of how many matters of particulate, and the imperceivable realms of which we have any comprehension. This really is ultimately a matter of perception since that's what any form of a definition begs for. A single person or group to determine exactly what the interpretation of a term will be. The way I personally see it is like this, "the more I learn the less I know" or in other words the better comprehension of how infinite matter, space, time, and their interactions becomes the more I understand there is so much possibility for that which I have no understanding, or even possibly the capability of grasping these theoretical concepts.

We would have to figure that no one means nothing with sound/vibration detectors. Would other plants count? Don't know how they would react to the "sound", but may curl or react if the vibration is strong enough. So, then, a lone tree falling in a wasteland. I'd say it died of loneliness!

Interesting! You might be right theoretically. Probably it's a matter of perspective and what definition you use for the conception "sound". I personally think that if there is some vibration in the air that possibly can be detected, in whatever way, there is sound. If it is actually received or not doesn't matter. Even if a person can hear it, it actually can't be proven anyway than with a detection device, because "hearing" is subjective. A deaf person, can't hear a sound, but doesn't it exist then?
And actually when there is vibration, how can someone make a definite conclusion that there is no sound if there is no one around? Who knows that there is no one, human or animal that can't hear it?

That question signifies, to me, the extreme anthropocentrism of our species! The sound is there and lots of other species with ears to hear it. It sounds to me like the comment "gravity exists in order to make it easier for us to sit down".

Check all tree falling cctv footages in youtube.
why only about tree falling??

We humans can feel the trees, but they don't feel us

When you say "no one" are you including all creatures? Trees fall down in the woods all the time where no human is around to hear but it still makes a sound that the woodland critters hear.

So heat an experience too. If iron is on and sitting on ironing board. And it is just there with no one around to sense it at all, it does not have heat. Would you say it has temperature but no heat? How far do we take the idea that an item of physics is an experience?

This is true. If a deaf person is standing by anything (a falling tree, crashing cars, etc) that person will hear no sound. Sound is produced by the brain converting wave vibrations in the air into sound. (IMHO)

So if a stove element is on and no one is around to feel it, it's not hot?

As strange as it may sound physics may have actually helped solve the question. Of course no one really quantum mechanics but the answer from QM seems to be that you are correct. The observer seems to be an integral part of the process we physicists call the collapse of the wave function.

I find it a little disconcerting actually. If no one observed it... yes, it is just a tangle of unobserved undetermined quantum states. So a "Schrodinger's box" of fallen and non-fallen trees.