Blackboard Collaborate Ultra is a live virtual classroom platform used by schools and universities for online lessons, meetings and lectures, and its end session tone is the built-in sound that marks the close of a session. Because so many students heard it daily in remote classes, the short clip began circulating on soundboards and in editing communities as a shorthand for school ending. It remains useful today because it is instantly familiar to online learners and instantly sets a classroom scene without any dialogue.