Mutes all civilian screaming, crying, phone calls, conversations, "you just stepped on my thousand dollar shoes!", "first I miss my train, now I'm getting robbed!", etc.
This also includes lines when they catch you trespassing, but I did not find those important.
Bliss.

If you just want to mute civilian lines when they are tied up, check out Jindetta.exe's mod here. (though I have not tested or looked at it)

payday 3 modding is painful