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

We have a VR system set up in our living room. I don't even want to talk about how long it took me to figure out the receivers were making a steady, high pitched noise. There are 4 of them and they are situated near the ceiling.

I hear it from a lot of things when it's quiet enough. Clock radios, tvs, monitors, my pugmill, heaters. There was a noisy power strip with a flashing one-off switch that I'm still convinced was going to kill someone.

I DON'T know anything about electricity - so mostly it makes me anxious that my house is going to burn down. I have bad enough hearing loss that I have to use closed captions on my TV - but it IS mostly because deep voices are extremely muddled. I'm surprised a bit by how many "not really" answers I see.

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

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

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.

Yes

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

I can hear my phone charging.

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.

I have like 2 USB chargers that are really loud.

Not after I stopped buying cheap power supplies.