Why do you think the title of the accompanying essay for the first three Modules of the course is, “Don’t speak until you’re spoken to”?
The command not to speak could be taken to mean the one giving the command is taking charge of a situation.
I think Alison’s point is a bit different. The command not to speak until spoken to entails consciousness of the fact that someone else is always already speaking before we do. If we spout off believing ourselves to be the first voice in the room, then we have passed over another voice without acknowledging it. In other words, speaking before you realize you have been spoken-to means there is an “unheard voice” to which you are not listening.