Sound Used: https://freesound.org/people/strangehorizon/sounds/676553/

From listening to the sound, we can hear 2 or 3 constant partials, with some slight ‘beating’ modulation, at about 4/5Hz. I’m listening thought laptop speakers, so I’m not sure if there is some noise mixed in as well (does sound like some irregular high-frequency content is present). There are no transients or impacts, its a drone.

From the spectrogram, we can see quite a few partials fading in and out, at regular intervals. There does appear to be some noise throughout, albeit quite regular.