what what what is all this about..... Sound is simply, very simply brought about by changes in pressure. The rate at which you vary the pressure will determine the frequency of the sound you here. Sound waves are (on this earth) waves of changing air pressure. In space - no air - no sound.
However, when in space firing an engine, matter is diplaced from the engine. If you are behind this engine you will probably hear it. However the sound waves will be waves of the combustion products and not air.
Relevant??
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