We all talk about the big bang as this moment the Universe begins by popping into existence with simple hydrogen and some helium. Hydrogen and Helium are gases that are able to carry sound. Today, space has expanded so much that there is vacume beyond where matter clumps together to form stars/planets, which means the sound couldn’t propagate, but the early early Universe wouldn’t have clumped like today; there would have been hydrogen everywhere. This means it would have been loud everywhere.
*Edit: I know we call it the Big Bang because of the rapid expansion of spacetime, but I always just pictured the general motion of expansion as the “bang”. Never thought of how loud it would have been.
Maybe how sound waves collided influenced how matter clumped?
Maybe the soundwaves colliding is one of the many reasons for these:
I think you have to differentiate between simple pressure waves or even shockwaves and soundwaves.
Like Michal said, usually something is only defined as sound if there is something to hear/interpret that sound. Otherwise it’s just waves in a medium, like any other kind of wave. What we humans consider sound and what a whale or a dog considers sound is not the same.
For the most part the beginning of the universe was very hot. Sure there was fluid dynamics going on, but would we consider that loud? Or just very hot?
As for the reason something essentially random had structure is very interesting, but I don’t think fluid dynamics or soundwaves had anything to do with it.