I guess four Conures would make more noise (and mess) than my one Conure, but I find Libby is very quiet for the most part, and she's really not that messy.
As an example, when I'm running the vacuum cleaner, she loves to whistle, chirp, and make other noises. I encourage her to do this, making noise right along with her! I find this helps her "let off steam". She makes a whistling contact call (not loud) for me now and then, and if I whistle back from wherever I am in the house, she's satisfied, and goes back to playing and talking to herself.
We don't have any children (we're retired), just 3 dogs, Libby and my Parrotlet, so generally our house is fairly quiet. When the dogs bark at the UPS man (they will NEVER get used to him!), Libby "barks" too -- a louder yell -- but stops immediately when the dogs stop barking and she sees she doesn't get any attention from it.
One last example, after lunch, we always take a nap. I say "naptime" and the dogs make a beeline for our bedroom. Libby climbs into her tent that's in her daytime cage and takes a nap too. When I get up, I whistle my contact call to her, she answers, pops out of her tent, and the afternoon begins!
Now she is louder than my Parrotlet, who just makes little "peeps", but still not noisy to me. All birds make "noise" of one kind or another, but to my old ears Libby's chatter is joyful and I love it!