21. Cars typically vibrate at a natural frequency of 15 to 25 Hz-- the higher the better. 22. The natural frequencies of a rolling element bearing with the free boundary conditions are 3 kHz. 23. Below the natural frequency , transmissibility hovers near 1. 24. Stepper motors have a natural frequency of operation. 25. Higher orders of parametric resonance are observed either at or at submultiples of the natural frequency . 26. Overtones occur when a system has more than one natural frequency ( as many systems do ). 27. Parametric resonance takes place when the external excitation frequency equals twice the natural frequency of the system. 28. It is also possible to test a physical object to determine its natural frequencies and mode shapes. 29. Where undamped natural frequency f _ 0 and Q factor are discussed above in the low-pass filter discussion. 30. Damping dissipates energy in the system, which reduces the vibration level which is transmitted at the natural frequency .
