Realtek - Droning audio hiss / whine, under specific conditions

I am using headphones, onboard audio. The sound is just a droning high-pitched hiss / whine with no variation once it's started, however it comes in different flavors (somewhat lower / higher pitch or volume).

For the sound to happen, it must meet one specific pre-condition: The volume must be un-muted, but there must be no output from any sources (music player, video player, streaming online audio, etc.) to my headphones. Any kind of output abruptly ends the hiss. Even given the pre-condition, though, the sound will not automatically be there. It is not constant at all times.

Some things that seem to cause the sound, given the above pre-condition:

(1.) Abrupt cessations of audio output. If, say, I'm listening to streaming audio on the internet, and the audio suddenly ceases for whatever reason, or if I directly stop it, this can trigger the hiss.

(2.) Changes in volume. If I shift the volume meter up and down enough, I can hear a horrifying assortment of hisses and whines. Most of the time, shifting volume doesn't bring the sound, but sliding quickly up / down the volume meter enough inevitably makes the sound pop up. Once the sound's started, shifting the volume from one level to the next always either changes the sound to a different flavor or kills it entirely. No particular flavor of the sound is associated with any level of volume. Any given flavor of the sound never itself increases / decreases in volume, but different flavors are louder than others.

(3.) Browsing folders. This seems rarer, but when I'm navigating through folders, going from one folder to the next can sometimes trigger the sound. Navigating to a different folder once the sound's started will change the sound's flavor / end the sound.

If the sound is triggered by any of these things, it will happen immediately, there is no delay.

Things I've tried, to no use:
-Reinstalling the Realtek drivers
-Messing endlessly with Windows and Realtek audio settings
-Using the direct rear jack on the motherboard rather than the front jack

Any help appreciated.

I've used different headsets, yes, which didn't help.

The problem started originally with the ASRock-supplied Realtek driver. I then uninstalled it and tried the generic Microsoft driver, same problem. Now I'm using the latest Realtek driver, and it's still the same.