well the ingame description for the life support says that the contdown is the time the existing athophere needs to leak, in that case we would ehar wind all the time form the air floating out of the cockpit outside by the air passing us. So somehow no desctiption truly fits to the implementation, it just somehow works xD
maybe because the sounds come from your drive section which is not in vacuum. vibrations propagate through the metalic structure rigth to your chair and your helmet ... which has an integrated 5.1 sound system
that may make sense but then there would be no reason to tone down the sound.