[ QUOTE ]
Amerocentricity is a beautiful thing.
Loudest sports fans? Soccer fans.
Biggest sports stadiums? Soccer stadiums.
You do the math.
[/ QUOTE ]
Well...
Indianapolis Motor Speedway - With a permanent seating capacity for more than 257,000 people [1] and infield seating that raises capacity to an approximate 400,000, it is the largest and highest-capacity sporting facility in history [2] (by comparison, the world's largest soccer stadium seats 150,000 spectators).
I have to imagine that it can get pretty loud in there...