Rub your 'f-u' finger against your top front teeth until it makes a sound. Then rub it against these two teeth back and forth in random starts and stops really fast, alternating with slower jerky movements - the room must be very quiet - soon you will discover it sounds a lot like people talking - perhaps in the another room, slightly muffled, but the pitch raises and lowers, and you can manipulate the effect, causing it to sound like women in the next room arguing or speaking excitedly. You hear the chatter, sense the emotion, but can't figure out what the hell they are talking about.
It even woke the cat up.
NB: Tomorrow's home-school project will involve rubbing the rim of your stemmed crystal wine glass to make it 'sing'. It is also 'wear-periwinkle-blue day' - so dress accordingly! We will also be reviving our fairy-tale-high stories for pre-school children.