Or the other version,
if a tree falls in the woods and nobody hears it, does it make a noise?
How many times have I heard this pseudophilosophical question? Too many.
So here is the answer, once and for all so that you can put the pseudo-philosophers at ease, although probably not, but at least put the issue to bed in your mind, once and for all, so you can stop losing sleep over the falling tree, and get on with your life.
First, does it make a sound?
Encyclopaedia Britannica ready reference defines sound as; "noun C.:mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium (as air) and is the objective cause of hearing"
Second, does it make a noise?
Encyclopaedia Britannica ready reference defines noise as; " noun B.: any sound that is undesired or interferes with one's hearing of something."
When a tree falls in the woods, it is in fact, the "object cause of hearing", whether it is actually heard or not. Yes, it makes a sound, whether someone hears it or not. In this universe, there are certain known constants of the physical elements within this universe. From atoms, to molecules, the speed of sound, the speed of light, and the known constants of elements within this universe, associated with motion, and associated with molecules that are closely connected, then separated. Absolutely it makes a sound.
However, a sound only becomes a noise, if there is somebody to perceived or hear the sound. I suppose, if a squirrel happens to be nearby, the sound also becomes a noise. However since squirrels don't speak our language, and we don't speak squirrel, were going to say it's a safe bet and a probability, that the squirrel heard the sound, and moved out of the way of the falling tree. I have never seen a squished squirrel under a fallen tree.
So there you have it. If a tree falls in the woods and nobody hears it, it does indeed make a sound, but unless somebody or some animal with audio receptors (ears/hearing) within the frequency and range, of that generated by a falling tree, hears it, it does not make a noise.
Toodles, philosophy heads