Mechanical resonance . It is a phenomenon that occurs when a body capable of vibrating is subjected to the action of a periodic force, whose period of vibration coincides with the period of vibration characteristic of said body.
In these circumstances the body vibrates, progressively increasing the amplitude of the movement after each of the successive actions of the force.
This effect can be destructive in some rigid materials like the glass that breaks when a tenor sings. For the same reason, troop bridges are not allowed to pass by marking the pass, as they can resonate and collapse.
One way to highlight this phenomenon is to take two tuning forks capable of emitting a sound of the same frequency and placed close to each other, when one is vibrated, the other spontaneously emits the same sound, due to that the sound waves generated by the first press through the air to the second.