There are a number of benifits in using the Operational Modal Analysis compared to the more traditional techniques.
Multiple Input Multiple Output Modal Technology
The Operational Modal Analysis are Multiple Input Multiple Output, MIMO, techniques. This means that the techniques are capable of estimating closely space modes and even repeated modes with a high degree of accuracy. Traditional modal anlysis techniques are typically Single Input Multiple Output, SIMO, or Multiple Input Single Output, MISO, or in the worst case even Single Input Single Output, SISO. Such testing procedures will not be able to find repeated poles due to the lack of mode seperation.
Easier Laboratory Modal Testing
There is no need for vibration shaker or impact hammer anymore. If you are in your lab doing modal testing in a test rig on some structural component, just do some random tapping on the structure while you are measuring the vibration response in muliple locations. The tapping must be random in time but also spatially. The excitation produced in this way will be a good approximation of a multivariate white noise stochastic process.
Winning Technology in In-situ Modal Testing
Vibration shakers and impact hammers are impossible as excitation sources when it comes to insitu testing of structures, such as buildings or rotating machinery. In cases like this the traditional modalanalyse fails, because there are a number of unknown input acting on the structures. What is a problem for traditional modalanalysis is a strength for Operational Modal Analysis. The more random input sources there are the better the modal results gets. Since the real strength of the technology really lies in the in-situ testing it is no wonder why the technilogy is called Operational Modal Analysis. Another important features that comes for free are that the estimated modes are based on true boundary conditions, and the actual ambient excitation sources.
Refrence: Structural Vibration Solutions A/S Co.