Created Friday 08 June 2012
Afterall, there isn't any in the naught.
The background hum of good spacecraft baffled not only to attenuate the sound, but also to modify it to be "binaural" sounds.
At one point, two craft approach. The one (the narrative is being written from) scans the other. The scanned craft is rich enough to be well-insulated so they can't detect what's going on inside or who/what is there. But, they scan the insulation and--after doing a quick calculation based on it and the craft's size, etc.--note that the baffling is set to filter sounds into a sleepful binaural state, thus inferring that the crew is sleeping.