A vibrator generates excitations by applying dynamic actions to the object. An electromagnetic vibrator (also referred to as a dynamic vibrator) is used for vibrating small structures. An excitation in simple term indicates this type. An electromagnetic vibrator functions over a wide dynamic range and enables individual adjustments of frequency and phase of excitation force and can perform excitation under several kHz.

The caution on using a vibrator and the most shortcoming of a feature of a vibrator are sudden decrease of the excitation force at the resonant point. This phenomenon is more evident under the object of lighter attenuation structure and lighter object. By this phenomenon, impact of noise increases at the important resonant point and the coherence decreases, thereby losing the measuring accuracy and reliability. In general, although no special attention is paid to the capacity of the vibrator, a vibrator that is as small as possible must be used if highly accurate measurement is necessary at the resonant point. In the normal vibrator, the basic natural frequency of the movable section exists under 5kHz or more (this is the upper limit of the excitation frequency).