What do you call this instance of break in noise?
You're in the gym waiting for the school principal to make a speech and everyone is talking, the whole place humming loudly. Suddenly it goes quiet because you all thought the principal has arrived, yet no one told you to be silent. Everybody else notices the others being quite and follows suit. Everyone is silent for a moment, but after they realize no one arrived and no one is enforcing the silence, the noise starts again. This has happened to me in classrooms and at seminars.
Solution 1:
lull - a temporary calm, quiet, or stillness