In nature, there are many mechanical components that are subjected to vibrations. When they are applied, the material is loaded by a certain level of stress, depending on their amplitude and their frequency. If those vibrations endure for long time, a possible structural failure could occur. Such type of failure, called also fatigue failure, happens as a result of accumulated damage. Most of the vibrations are non-deterministic vibrations or, so called, random vibrations. They are non-deterministic excitations, a type of oscillation whose behavior is non predictable and without repeatability. The unpredictable behavior of those vibration makes the work of the designer complicated.