resonance

4.04  resonance. Phenomenon that exists for a linear system in harmonic forced oscillation when any change in the excitation frequency results in a decrease in the response of the system.

Annotation 1                  The harmonic forcing frequency(ies) is near that of a modal or natural frequency(ies).

Annotation 2          The quantity that is the measure of response should be indicated (displacement, velocity or acceleration). Velocity resonance, for example, may occur at a frequency different from that for displacement resonance; see Table 1.