Neyland, Tiger Stadium, Bryant-Denny, Sanford, almost all stadiums aren’t built or designed to hold in noise. They’re designed and built based on the footprint of land available. BDS has been expanded multiple times from the initial capacity of 12,000. The expansion has resulted in many structures being demolished on three sides of what exists now. During these expansions, it would have cost much more to change the slope of the stands to retain crowd noise.