Sympathetic resonance or sympathetic vibration is a harmonic phenomenon wherein a formerly passive string or vibratory body responds to external vibrations to which it has a harmonic likeness. The classic example is demonstrated with two similar tuning-forks of which one is mounted on a wooden box

https://en.wikipedia.org/wiki/Sympathetic_resonance

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Note added at 5 hrs (2016-09-07 10:20:55 GMT)
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Sympathetic Oscillations

example of sympathetic oscillations is furnished by the so-called “coupled pendulums

https://books.google.com/books?id=cKFmDAAAQBAJ&pg=PA106&lpg=...

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