Technically, in space, you wouldn't be able to hear the sounds of blasters and engines etc. because the sound has nothing to travel through. I know every work of science fiction has made the mistake (with the exception of Firefly/Serenity), but in Star Wars, I believe there may be a way to explain it.

Please note that I'm not a physics expert, so I am most likely wrong.

In most of the Star Wars novels it says that after a blaster has been fired, it emits the distinct smell of ozone. So when a blaster is fired, a gas of some sort is released.

Therefore, in space combat, after a few shots have been fired, there is something for the sound to travel through. You can only hear the sound if you are directly inside the battle.

The engines, however, are much easier to explain. The sound that you can hear is not the sound an onlooker hears, but actually the sound that the pilot hears. This is the case in Firefly/Serenity.

I know my theories are idiotic, but they just might work. So please tell me your thoughts on the matter.