I booted into a bare-metal 18.04 system today, and while making some notes on a few things it was (very and unpleasantly) clear that about half the time that I hit the down arrow when already at the end of a document, I'd get a clipping / crackling sound from the speakers I have plugged in.
"Alert volume" is muted, so even if pluma was trying to beep - which it had damn well better not be, since that's ridiculous behavor - it shouldn't go through anyway. But it's clearly happening.
What's also interesting about this is that it's inconsistent. The SECOND time I press the key, nothing happens. But if I leave the window alone for a little while (like now, when I'm actually in a VM) and then go back to it, I get the pop / crackle / whatever again. It's like it's powering down the speakers, then powering them up again to (not) play something.
I doubt this ever happened in 16.04, since it's so obnoxious I couldn't possibly have missed it, but I don't generally have the speakers powered up on this machine so I'm not 100% sure on that.
Has anyone else come across this? Is there something ■■■■■■■■ in PulseAudio that keeps screwing around with the sound buffers or power like that?
(Incidentally, pluma in this 16.04 VM doesn't trigger the problem: it's only the 18.04 bare metal one that has it).