It really depends on what you personally consider loud or too frequent. For example, tiny Budgies can be both surprisingly loud for their size (when having a screaming fit) as well as frequently noisy singing and such. They drive me nuts, while some people don't mind at all. I personally dislike the Cockatiel sound.
Parrots are vocal creatures in general, so let's say you'll tolerate a "reasonable" amount of noise. As far as frequency of noise making, some species generally speaking are more vocal, but then some individuals (within the same species) are much less vocal than is typical. That can be because of training, socialization, environment, AND individuality.
As far as how loud in volume, depends on species. BUT what volume or pitch you can personally tolerate is something of course you'll have to determine yourself after hearing different parrots first hand.
For example, I have heard people say before, that some of the smaller Poicephalus (Senegal, Meyer's, Red Bellied, etc) are loud, but personally I don't agree at all! In fact their call is really wimpy IMO lol. Loudest is sort of a high pitched whistle, but NOT even near as loud or piercing as a conure.
Pionus are considered quiet. Raven is quiet, but I've heard him yell, and I used to have another Pionus, so I know what they sound like. Some people say Pionus are loud. I don't agree... Even a Pionus screaming full blast is NOTHING compared to most parrots. Still people will say they can be loud. See? It really depends on the person's opinion of what loud is
There is a Goffin's cockatoo who lives next door... Now he is LOUD and the pitch is very RASPY and hard to listen to. But that's only MY opinion. His owner can tolerate it (though she admits he's obnoxious haha)!