Time for a bedtime story before you can close your eyes. Since it has been a long and tiring discussion about the main reasons behind what is better: 432 Hz and 440 Hz. To be fair and honest here the main answer would be : "what sounds best for you!". Period and end of discussion.
But since this constantly comes back and it leads to a lot of misconceptions about the whole 440 Hz vs 432 Hz thing. Some people say it is the universal sound because it is in tune with the universe. Others compare it with the fibonacci sequence (where I have no idea where this comes from because it just does not make any sense). Others totally mix up the meaning or the definition of 440 Hz and why 432 Hz was ignored. So... With that intro out of the way, lets talk facts and forget the rumors.
To get a full understanding (and bore you to death in the process) about the different frequencies is to understand where all these different frequencies comes from. The 432 Hz originally (at least some claim) that it comes from Pythagoras (a Greek philosopher, mathematician and scientist). He defined music in such a way which was later to be known as Pythagorean tuning.
Pythagorean tuning is a mathematical formula translated to a 3:2 ratios and 2:1 ratios which defines the intervals frequencies. Later on this idea was used to create musical instruments and the so called perfect fifth was born. I could just write down the complete history down from 500 BC till now what happened with it. While in theory this is all ratio based there is no given prove about that his tuning process lead to A=432 Hz. The tuning process (in general) would be one of the standards we would get to know in music. It will get more complicated then this.
Meanwhile in Germany (1600-ish) there was a different tuning for instruments. This would be A=567Hz for simple pipe organs. While Mozart would use 421Hz or 422Hz for tuning the instruments. Parts of it are in this PDF document which is a segment from the book : studies in the history of musical pitch. While there were different frequencies and different pitch, some point during word war 2 the native A pitch was changed to 440 Hz in Europe and the United States. This would later on lead to world issues. The major problem that occurred was this: people who play an Oboe in France could not play in an orchestra from China. The same thing could be said for instrument exports and so on.
This is one of the reason why a global standard was introduced (not because the Nazis made it, but it was a global initiative) and this would later be known as ISO-16 (registered on 1975).
So the whole 440 Hz is a standard while 432 Hz was a mathematical formula. And this by itself leads to a lot of fiction. So everything above is based on 'facts'. History even. Some of these are written in books, others have written down studies. Yet there are people who have had feelings about "things" which leads to a lot of speculation and so on.
And this is where we'll continue with some fictional vs facts.
Fictional: Ancient instruments were tuned in 432 Hz. Because they needed to be 'puuurfect'.
Fact: Hertz is defined as one cycle per second and was scientific named by the German physicist Heinrich Hertz in the late 1890s. While the theory was originally proven with the Tonometer made by Johan Scheibler back in 1834.
Fictional: Because water creates cool shapes on 432 Hz, it is there for defined as the natural sound.
Fact: Sand does the same but on 345Hz. And sand is a natural product too.
Fiction: Pythagoras A=432 Hz
Fact: Pythagoras used ratios to define the pitch differences between two notes. No one really knows the base note which he used a reference (unless you have an original Pythagoras Bell, then you will be the first).
Fiction: 432 Hz is based on 8Hz which is defined as our DNA, The World, the Universe and everything else.
Fact: the base frequency of Earth Heartbeat is proven to be 7.83 Hz (As defined by a case study made by a physicist called Winfried Otto Schumann. If you multiply 7.83 Hz the closest you'll get is to 430.65 Hz.
Fiction: 432 Hz is part of the Fibonacci sequence
Fact: No. It is not. 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418, 317811. In comparison here are all the musical notes in Hertz. Some would say that 8 is a part of the sequence, while in theory this would be 8.02 to be exact.
While there is a lot of debate weather 432 Hz is the define universal frequency, or it is 440 Hz, it really does not matter. All we know by now is that 440 Hz is adapted as a standard due to events that happened in the past. And history basically told us in the long run that we had to pick a number. While there are different scientific studies that would certain elements to be in sync with a specific number (for instance there is this water flow on 24 Hz, is this the base note now?) it just happens to be an agreement we make for ourselves as artists among each other.
Just to recap this in a Video format, I found a descent video that kind of recapped most of the important events till this day on how we really got here:
Written by hydlide