Use a spectroscopic app on your phone

It'll help you identify the source of high pitch sounds

I once noticed an external HDD was making a high pitch noise intermittently, as the LED turned on and off. It was bizarre

Edit: spalling

I can't hear it but I can often tell when it clicks over because it causes a spike in my tinnitus.

I really only notice them when the rest of the room is silent. Otherwise my brain ignores the sound most of the time.

It is never quiet enough in my house to hear myself think without difficulty, so it definitely never gets quiet enough for that.

My monitor has a power led that blinks when in stand by (and not receiving a signal.
And the coil whine between the onn/off-switching is audible.

When my monitor is on stand-by the led slowly blinks and every time it turns on I can hear it. Aside from that, I don't think so.

Ugh. Now you got me thinking about hearing my heart beats.

Everyone with fully functioning ears can hear it if they pay attention. Just a reminder to protect your hearing!

Inside your ear are hair cells that detect sound. You're born with the only hair cells you'll ever have, and damage to them is irreparable. Hair cells naturally sustain damage over time and people's hearing decreases as they age. This process is accelerated if someone constantly listens to things at loud volumes. So, maybe don't turn it up to 11!

Yes all the time

Yes

Even past 30 and with (mild) tinnitus, yeah my hearing is still great so I'm going to hear it. Light bulbs, chargers, the router etc.

Recently my computer's PSU has started randomly buzzing a not-quite-high frequency. It could be age (it's from 2019) though I'm pretty sure it's some kind of interference because sometimes it won't make any noise at all for days and I'm pretty sure my light bulb (an LED filament bulb which doesn't have much in the way of components) seems to also make different pitches of buzzing that coordinates with how much my computer PSU will buzz.

Anyways it bothers me, so as soon as I post this I'm going to power-down and unplug my computer and switch to a different device for the next day or so.

My friends and I used to drive out to an area of the desert, away from people and the general noise of civilization. However, there were large power transmission lines going through the area and we could listen to them crackle in the night as we watched the stars. Just a nice way to relax and get away from it all.

I can’t of anything that makes an unwanted sound. Old CRT TVs used to, but I haven’t used one in years. My monitor at work makes a sound when it turns on or off (I believe there’s an ass-old fuse in there), but it makes no sound otherwise.

I’m still young and hear very well, as exemplified by my annoyance of half-closed bottles of carbonated drinks, which do make a sound.

Not after I stopped buying cheap power supplies.

I have like 2 USB chargers that are really loud.