I don't know, but from what I've seen of bantam roosters, they have a little man complex and like to crow a lot. And boy can those little ones belt it out!
i agree bantams are really loud but the least loud would have to be the serama... when it crows it makes the sound equlivent to a small dogs bark. I persobally like the breed and their crow doesn't seem to bother me, here is the breeds background http://www.jerrysseramasllc.com/american.htm