Are underage witches & wizards allowed to send Howlers? How does a Howler work (the sending part; we know the receiving all too well)? It's got the body of a letter, so presumably paper is involved at some point, and it's got the recorded (interactively recorded?) voice of the sender, it's got a timer function (x amount of time after delivery still unopened, and it explodes), an explosion function (obviously), and it's got variable volume (louder if exploded than opened).