Going into my second year with them, I don't find them THAT noisy overall. When they get about 3 months old they start freaking out about everything, and it takes them a couple months to figure out what's really a threat and what isn't.
The only time they're consistently noisy is late winter / early spring when they get ready to pair off. This is also if you keep them with chickens they'll drive them crazy. The males start charging at literally everything and the females loudly make their two-tone "guh-wahk" calls constantly.
The rest of the year they're pretty quiet. Guineas never really shut up, but most of the time it's a series of quiet hoots, chirps, and clicks. They only get really noisy when they go into "red alert" mode. I live on 16 acres and I'm not near any busy roads, so when they do sound off it's usually something real, even if they're only harrassing deer or chasing the wild turkeys away.