System Error Noise

such as when u hit final result in a file doing ^F.

WHERE do u turn this down?!

settings>system>sound has nothing relevant.

"sound mixer" settings (which i have to get via search; how does it relate to the FIRST one?? not seeing a link there) has the exact settings i'm looking for: "system sounds" and "MS edge sounds" sliders, but they don't seem to "take". i reduce one or the other to 5%, say, but upon next check they're both back to 100%!

in the short term i've found a DIFF place:

settings>system>sound>sound ctrl panel>sounds>sound scheme

where i can set the whole system to "no sounds". works great, but perhaps overkill; rly would rather have them ON but at some extremely low volume.

am i missing something? such as how to get the 2d option to "take"?