Description:Adding a small clamp onto one of the tuning bars reduces its frequency. Striking two tuning bars, one with a weight, then produces beats. The frequency of the beats can be adjusted by varying the position of the weight on the bar.
Without weights on either bar, strike one of the tuning bars, then hold the other adjacent to the struck bar for a few seconds. If the struck bar is then damped, the sound continues. The second bar is in resonance with the struck bar, and some energy is transferred if they are physically near each other.
This demonstration is similar to demonstration H2-52, except for use of open tuning boxes for resonance. It is a bit louder for use in the lecture halls, but perhaps a bit harder to explain because of the resonant boxes.