Since we don't know how the propulsion, power generation, weapons or even "radios" work in scifi we can't say that a person in space couldn't hear the "radio" emissions from things in space. Even if "sounds" (emissions) weren't coming through their "radios" they could still be picked up by the structure of the ship or some piece of equipment. Even a rock drifting by could be heard if the rock was emitting radiation or if the "radio" used some kind of gravitational or spacetime process. A person being "spaced" could probably hear his own blood or fluids in his ear boiling.