Observe a demonstration of Matching Resonating Boxes from the Physical Science Collection at the Smithsonian's National Museum of American History. This set of resonance bars, each with its' own resonator, can be used in an interesting demonstration. First, because the bars are physically identical, they both have the same resonant frequency. And that sound is strongly amplified by the wooden resonators on which the bars are mounted. In the demonstration, the two instruments are placed some distance apart and the first bar is struck sharply to make a tone. Because the two bars are identical, the second bar will respond to the sound of the first by making the same tone. If the first bar is damped, so that it no longer makes a sound, it will be noticed that the sound is now being produced (faintly) by the second bar. The second bar "resonates" with the sound of the first.
