In physics, the relatively large selective response of an object or a system that vibrates in step with an externally applied vibration. Acoustical resonance is the vibration induced in a string of a given pitch when a note of the same pitch is produced nearby, in the sound box of an instrument such as a guitar, or in the mouth or nasal cavity when speaking. Mechanical resonance, such as that produced in a bridge by wind or by marching soldiers, can eventually produce wide swings great enough to cause the bridge's destruction. Resonance in frequency-sensitive electrical circuits makes it possible for certain communication devices to accept signals of some frequencies while rejecting others. Magnetic resonance occurs when electrons or atomic nuclei respond to the application of magnetic fields by emitting or absorbing electromagnetic radiation. See also nuclear magnetic resonance.
"Mechanical resonance is the tendency of a mechanical system to respond at greater amplitude when the frequency of its oscillations matches the system's natural frequency of vibration (its resonance frequency or resonant frequency) than it does at other frequencies. It may cause violent swaying motions and even catastrophic failure in improperly constructed structures including bridges, buildings and airplanes—a phenomenon known as resonance disaster. "