damped natural frequency

4.10  damped natural frequency. Frequency of free vibration of a damped linear system. Unit, hertz (Hz).

Annotation              Oscillation of a damped system may be considered periodic (see 2.09) in the limited sense that the time interval between zero crossings in the same direction is constant, even though successive amplitudes decrease progressively. The frequency of the oscillation is the reciprocal of this time interval. See Table 1 for examples.