After 15 seconds the audience laughs. Paul holds the ringing aluminum rod. Sound is the organized motion of the rod. The organized motion is converted into heat and the sound fades away. Aluminum rods turn the organized motion into disorganized motion very slowly, they can ring for over a minute.
Fingers turn organized motion into heat.
I hold the rod at the middle and hit it on the end. I grab the end between two fingers and the rod stops ringing immediately. I hit it again and grab it near the middle, it keeps ringing. Your fingers tell you where the rod is vibrating. If you grab it where it is vibrating, the sound goes away.