So I think the real question your asking here is if sound could make it all the way to the top of our atmosphere? If space suddenly had the ability to transmit sound, that sound would first have to travel through our atmosphere to reach space, or the atmosphere itself would need to make sound to transmit to space.

Assuming the atmosphere still thins with altitude before it reaches “magical sound transmitting space,” then the atmosphere itself won’t be able to carry sound that high. At a certain point, the air will be so thin that sound just won’t be transmitted through it effectively, and even though sound can travel through it, it won’t travel very far. By the same logic, that thin outer boundary of atmosphere won’t be able to efficiently transmit sound into magical sound space.

You could imagine that the atmosphere itself would make noise to. Wind and atmospheric phenomena all over the earth would make a ton of noise. But again, the thinning of the atmosphere would largely contain this to earth.

Basically, sound would travel far for the same reason it doesn’t travel at all in a vacuum, there isn’t enough (or any) physical medium to put that sound out into space at the edge of our atmosphere.

Yah the trick that works for me is just to not think about it too hard or else I risk full existential crisis.

A metaphor I’ve always liked is the raisin bread one. In this metaphor, the raisins are galaxies, and the dough/bread is space-time. When you bake the loaf, the dough rises and expands. And once the loaf has finished baking the raisins are now farther apart than when they started. But they aren’t farther apart because they moved through the dough away from each other. They are farther apart because the dough expanded. The substrate they exist in expanded, space between them expanded, and now they are farther apart.

So when we talk about the universe expanding, we aren’t talking about galaxies simply drifting farther away from each other. We are literally talking about space itself expanding. The emptiness itself between galaxies gets bigger. And that process can happen faster than the speed of light.

It’s also worth noting (and I’m not that up to date on this so someone correct me) that the Big Bang isn’t like everything just started expanding from a single point at the speed of light. It’s more like all of a sudden everything just was. Not instantaneously, but in a matter of seconds the early universe just was, and it was big (millions? Billions? of light years big). And from that point it began to rapidly span outwards. And again, the Big Bang wasn’t all of a sudden matter exploded into the empty space-time of our universe. The Big Bang created our universe. It created space. Before it there was nothing. Not nothing like empty intergalactic space nothing. I mean like no-such-thing-as-empty-space nothing.

So yah the universe can expand that much in a short amount of time.