Natural frequency, measured in terms of eigenfrequency, is the rate at which an oscillatory system tends to oscillate in the absence of disturbance.
The phenomenon of resonance occurs when a forced vibration matches a system's natural frequency.
In a mass–spring system, with mass m and spring stiffness k, the natural angular frequency can be calculated as:
[2] Natural frequencies depend on network topology and element values but not their input.
[4] A pole of the network transfer function is associated with a natural angular frequencies of the corresponding response variable; however there may exist some natural angular frequency that does not correspond to a pole of the network function.