reminds me of when us students were accused of too raucous behavior in French class. So the teacher got a gettoblaster and put it on our desk with a tape in and set it to record!
We had a bit of weird teacher at school; fat (short arms, big belly - so had to write is semicircles on the board), mad, would fart in the wastepaper bin. He had poor class control and world also just wander out of class of ages leaving us to our own devises.
One day he's disappeared and we're all rattling away - the door opens, he comes in, opens a draw and pulls out a dictaphone.
Re-winds the tape a few seconds and plays it back..... noisy school kids...... door opens.... silence.
"You hear that silence? Thats the sound of power" he said
It wasn't - it was the sound of us expecting someone with some actual authority coming in to ask where the hell our teacher had buggered off to again.