Multi-Reference Modal Testing

A multiple reference modal test is done using either multiple (fixed) exciters with sensors to measure the forces, or multiple (fixed) response sensors.
Each fixed sensor is called a Reference.

Multiple Shaker Test

In a multiple shaker test, two or more (fixed) shakers are used to simultaneously excite the structure.

Large structures with non-linear dynamic behavior are typically tested using multiple shakers, driven by pure or burst random excitation signals
Random excitation together with spectrum averaging is used to "average out" the non-linear dynamic behavior of the structure from the spectra and hence the FRFs.

Multiple Reference Roving Impact Test

In a multiple reference roving impact test, two or more (fixed) response sensors are used, and the structure is excited one DOF at a time with a roving impactor.