But someone could have a huge flat speaker to make a humming noise and influence the vote!
Well since there's no roll call or concept of membership at ietf a more real problem is companies flooding the room with their employees for critical votes.
What is humming for consensus you ask? Well, rather than a show of hands, when deciding on measures and proposals they simply ask the room to hum in favor of a measure.
The reason is simply that even if you are sitting next to your boss it will still be possible for you to vote according to your conscience as it's virtually impossible to distinguish the direction of humming in a room of a hundred or so people. It is, however, easy to tell if a measure has the majority support of a group via humming.
It's very geeky and very smart. Very IETF.