Loud boisterous reactions are not the only sign that you have connected with your audience though. Different people react very differently to the same effect. While you might get one person who will scream and stamp around at a rising card sequence. Another person may internalize there feelings and just (as Flyspazz put it) stand there looking like their "brain(s were) scrambled like eggs on Sunday morning." Both of these reactions are legitament signs that one has connect with his/her spectators. The reactions have as much to do with the psychology of a person as the effect itself.