Vibrating objects are always subject to all kinds of resistance. The existence of damping causes the mechanical energy of the vibrating object to be continuously converted into other forms of energy and consumed, and it propagates outward in the form of waves, so that its amplitude is continuously reduced and the vibration finally tends to stop. This process is the influence of damping on the structural response of objects.

An object is forced to vibrate under the action of external force. When the amplitude reaches the maximum, it is called * * * vibration. Due to the existence of damping, the vibration frequency is less than the natural frequency of the vibration system. When the damping coefficient is small, the vibration frequency of * * * is closer to the natural frequency. In real life, the natural frequency is approximately regarded as the * * * vibration frequency of a vibration system.