I legitimately became curious and wondered if what I had in mind was the actual answer to this peculiarity. Turns out I'm right... they're only measuring the frequency of the energy that basically every single object resonates with/produces.
Spoiler Alert: Even though there's no air in space, planets, stars am other spatial bodies generates vibrations that can be converted into sound, hence they "produce" sound.
I remember reading something like: "Plants leafs tweets"... literally a plant that posted on Tweeter or something along those lines... maybe I'm mistaking ut with pain detection in plants...
Fun fact, static on radios and old televisions are remains of electromagnetism and radioactive energy produced by the theorical event called Big Bang.