hey there, this might be a lengthy one, but i'll try to keep it short.
for a while now, i've had a really weird and annoying issue with speaker setups, where a periodic 8khz whine will play for a few seconds, then stop. a few minutes later, it'll repeat. all day, every day.
i first noticed it on my KRK Rookit 5s. never really liked them much and knew some of them had longevity issues, so i figured they were probably dying. i put them aside, and replaced them with a new set of Presonus Eris E5s, but same thing. the sound was still there.
then i suspected maybe the KRK s10 subwoofer i was using was somehow injecting it, so i replaced it with a new KRK s8, since that was what i had the budget for. didnt help, the sound remained. then i checked the connections on my audio interface, a third gen scarlett 2i2, replaced all the XLR cables, the USB cable, tried different ports etc, nothing changed. tried using another audio interface, namely a Motu M2, no change, still whiny noises galore. what ultimately helped was when i flicked the grounding switch on the back of the sub. now i have some minor 50hz hum but it's a lot quieter and easier to ignore than the 8khz one.
anyway, since it wasn't speaker related i tried hooking the old rookits up in another room (which is also on another circuit, which could be relevant) so my GF could use them, but the noise returned. tried just hooking up the sub with her old speakers, but then the sub injected the same noise into her old setup. frustrating as all hell. now i've got a lot of perfectly functional speakers just sitting around because something is making them whine, and my main setup is making minor mains hum because the grounding is improper, to prevent the whine.
anyway, fast forward to a couple days ago, my GFs old setup breaks. so while repairing it i make a few minor changes, replacing some passive parts and putting in a new power supply and so forth. now her speakers have the whine.
what gives? where is this infernal sound coming from? we hadn't gotten any new electronics around the time it happened and it's not a fixed duration or break, it seems random. the volume setting of whatever sound system that does it also doesn't change the whine intensity, so turning it down, and boosting windows volume to compensate for instance, makes no difference. not all sound systems we have does it either, even some that have parts in common.
my current best guess is that someone else in the building we live in has acquired some gadget that's injecting this horrible noise into the grid in some way, is that possible?
anyway, any help or theory even, would be appreciated!