Fault diagnosis of Massey Ferguson gearbox using Power Spectral Density

Many vibration environments are not related to a specific driving frequency and may have input from multiple sources which may not be harmonically related. Examples may be excitation from turbulent flow as in air flow over a wing or past a car body, or acoustic input from jet engine exhaust, wheels running over a road, etc. With these types of vibration, it may be more accurate, or of more interest to analyze and test using random vibration.