When you think of loud fans, you don't normally think of baseball.
Thoughts of an accountant dressed in Road Warrior gear, or a elementary school teacher wearing golden pigtails with Vikings horns, are what comes to mind when I think of loud, rowdy fans.
Ranking the loudest fanbases of the MLB teams is kind of like ranking which NHL fans are the best dancers, or which NBA team's fanbase is the most avid outdoorsmen. The two don't really go together.
At a football game, I can't understand what the guy next to me is saying most of the time. At a baseball game, I know exactly what the couple ten rows behind me is fighting about
Passionate, knowledgeable and maybe sometimes tased—these are words I think of when I think of baseball fans. But baseball fans are the most reserved of the four major sports in my opinion.
That's not to say baseball games never get loud. But because of the nature of the game, the moments to cheer are just more rare than in other sports. Still, during those moments, there are fanbases that can tip the scales in the favor of the home team.