Resonance & Rice

[Alex]

Here is my understanding of resonance:

Resonance is when the frequency of one thing matches the natural frequency of another allowing for a much greater transfer of energy from one to the other.

To my understanding that demonstration is not of two vibrations in synch but rather simply (though still coolly) a visualization of the vibration of just one thing, the vibration of the soundwaves as they pass through the board.

I have no problm accepting that I'm probably wrong. Just trying to piece together why.