Curb your expectations. You’d have to take your helmet off to hear “space sound”. Seriously, the article uses a pretty wide definition of “sound”, IMO. Sure, a non-complete vacuum can transport vibrations in some way, but sound? Sound is what you actually can hear. Anything else is oscillation. Sure “human standards are not a great basis for comparison” but sound, specifically, is a human standard or at least oscillation within a medium you can put your ears in on onto. Otherwise any oscillation from gravity waves or the “noise” of a travelling glacier to electromagnetic radiation could be considered sound.