Sounds in space is pretty easy to justify for the actor, observer and the acted upon.
actor- you firing your weapons, thruster, effects, etc..... create the sound when you use something on/as a part of your ship
observer- sensors translate what they observe into information for the the viewer: hud s, flashing colors and sounds are just a few possibilities
acted upon- when struck by an opposing ships weapons, thruster plume, or wandering objects they act upon and create a sound using your ships atmosphere.
None of the sounds created actually has to be similar even if they were all from the same source only the observer would really be able to choose what sound represented or resulted from an action but in all cases you could be an observer while simultaneously being one or both of the others.