Everybody remembers Pluto's demotion to dwarf planet in 2006. This reclassification was triggered by the discovery of Eris, an object far out beyond Pluto's orbit that was found to be 27% more massive than Pluto. So either it had to be the tenth planet, or Pluto shouldn't classify as planer either.
There is no sound in space as vacuum doesn't transmit it. There is nothing the sound waves could move through. So it's pretty silent out there.
That is actually a good thing. Our soundscape would be quite different if we could hear the loudest sound in our solar system. Despite being 150 million kilometers a way, that huge explosion in the sky that we call sun would generate a sound that would hit us at 125 Desibels. That's about the same as a sound of a jet engine from a close distance. So it would be quite deafening.