What is the term for amplification when driving frequency matches a natural frequency?

• A. Damping
• B. Natural frequency
• C. Harmonics
• D. Resonance

Answer: (D)

Resonance is the term for amplification when driving frequency matches a natural frequency. When the forcing frequency equals the system’s natural frequency, the input energy adds to the motion in phase with it, so each cycle builds on the previous one and the amplitude increases. Real systems aren’t perfectly lossless—damping dissipates energy—so the peak is finite rather than infinite. The natural frequency is simply the system’s inherent vibration rate, damping is about energy loss, and harmonics are integer multiples of a fundamental frequency that can excite other modes. But the specific boosting of vibration by driving at the natural frequency is resonance.