Modal analysis

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Modal analysis is the study of the dynamic properties of structures under vibrational excitation.

Modal Analysis, or more accurately Experimental Modal Analysis, is the field of measuring and analysing the dynamic response of structures and or fluids when excited by an input. Examples would include measuring the vibration of a car's body when it is attached to an electromagnetic shaker, or the noise pattern in a room when excited by a loudspeaker.

Classically this was done with a SIMO approach, Single Input, Multiple Output, that is, one excitation point, and then the response is measured at many other points. However in recent years MIMO has become more practical.

Typical excitation signals can be classed as impulse, broadband, swept sine, chirp, and possibly others. Each has their own advantages and disadvantages.

The analysis of the signals typically relies on Fourier analysis. The resulting transfer function will show one or more resonances, whose characteristic mass, frequency and damping can be estimated from the measurements.

The animated display of the resonance is very useful to NVH engineers.

The results can also be used to correlate with Finite Element Analysis.