I uploaded the vid as an unlisted YouTube video to send here it is
My PSU makes this sound but only in the middle of the night for some reason even when unplugged.
youtube.com
Whatever frequency it is, it definitely triggers a pretty
basal feeling of dread/concern.
I hope I'm safe in assuming it's
artificial, but it
sounds like the guttural noise of a med-large predatory mammal.
On the EMI angle: Do you have an old AM radio handy? I often can manually 'sweep' the AM band and 'hear' things like radiated emissions from A/C compressors and cheap LED bulbs.
Kinda edging into
crazytown, but... Do you have any frenemies or mischievous friends w/ extensive electronics/radio knowledge? This seems like it could potentially be a '
(inverse)phreaking prank'
I have to admit, if I knew how to make electronics sound possessed at a distance, I might do just that.
Another (even more remote) possibility:
Infrasound, attenuated into the audible range by reverberating in the case's construction.
It's a longshot, but I suppose your room
could be a 'node' for infrasound from Wind Turbines (or something) nearby.
Doesn't much explain why it's only at night though. I can imagine a reason, but it pushes things even further away from "realistic probability'
Does it make the
same sound
anywhere you put the computer? Like, say the bathroom?
(Bathrooms often have
unique acoustics vs. the rest of ones' living space.)
you should just get a new psu, then set this psu up so that it's on a live stream.
If it is caused by an external force
(and not literally a possessed/cursed piece of technology) I'd bet it'll stop once removed from the case. I can hear the metal of his case reverberating in addition to
le spooky noise. The case
sounds like it's part of what's
generating the sound.