It depends on the sound and the speed at which you run them. Guys should at least run 40 yards in 4 seconds or less. Any longer than that (remember the Miggle/NFL Films clip???), it's not fast enough. Some leagues emphasis 70 yards (from the Kick Off team's 30 yard line) in 4 seconds or less. Oh yeah, WITHOUT the guys falling over, obviously. Now, once you get that down, you'll have to compare the noise. Speed and noise are the 2 factors. Good luck.